Optical Disc

Optical Disc

incomputing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc which encodes binary data (bits) in the form of pits(binary value of 0 or Off, due to lack of reflection when read) and lands (binary value of 1 or on, due to a reflection when read) on a special material (oftenaluminium) on one of its flat surfaces. The encoding material sits atop-a thicker substrate (usually polycarbonate) which makes up the bulk of the disc and forms a dust defocusing layer. The encoding pattern follows a continuous, spiral path covering the entire disc surface and extending from the innermost track to the outermost track. The data is stored on the disc with a laser or stamping machine, and can be accessed when the data path is illuminated with a laser diode in an optical disc drive which spins the ditc at speeds of about 200 to 4,000 RPM or more, depending on the drive type, disc format, and the distance of the read head from the center of the disc (inner tracks are read at a faster disc speed). The pits or bumps distort the reflected laser light, hence most optical discs (except the black discs of the original PlayStation video game console) characteristically have an iridescentappearance created by the grooves of the reflective layer. The reverse side of an optical disc usually has a printed label, sometimes made of paper but often printed or stamped onto the disc itself. This side of the disc contains the actual data and is typically coated with a transparent material, usually lacquer. Unlike the 31/2-inch floppy disk, most optical discs do not have an integrated protective casing and are therefore susceptible to data transfer problems due to scratches, fingerprints, and other environmental problems.

 Optical discs are usually between 7.6 and 30 cm (3 to 12 in) in diameter, with 12 cm (4.75 in) being the most common size. A typical disc is about 1.2 mm (0.05 in) thick, while the track pitch (distance from the center of one track to the center of the next) is typically 1.6 urn.

An optical disc is designed to support one of three recording types: read-only (e.g.: CD and CD-ROM), recordable (write-once, e.g. CD-R), or re-recordable (rewritable, e.g. CD-RW). Write-once optical disc. cornmonly have an organic dye recording layer between the substrate and the reflective layer. Rewritable discs typically contain an alloy recording layer composed of a phase change material, most often AgInSbTe, an alloy of silver, indium, antimony, andtellurium.

Optical discs are most commonly used for storing music (e.g. for use in a CD player), video (e.g. for use in a Blu-ray player), or data and programs forpersonal computers (PC). The Optical Storage Technology Association (OSTA) promotes standardized optical storage formats. Although optical discs are more durable than earlier audio-visual and data storage formats, they are susceptible to environmental and daily-use damage. Libraries and archives enactoptical media preservation procedures to ensure continued usability in the computer's optical disc drive or corresponding disc player.

For computer data backup and physical data transfer, optical discs such as CDs and DVDs are gradually being replaced with faster, smaller, and more reliable solid-state devices, especially the USB flash drive. This trend is expected to continue as USB flash drives continue to increase in capacity and drop in price. Similarly, personal portable CD players have been supplanted by portable solid-state digital audio player (MP3 players), and MP3 music purchased or shared over the Internet has significantly reduced the number of audio CDs sold annually.

History

The optical disc was invented in 1958. In 1961 and 1969, David Paul Gregg registered a patent for the analog optical disc for video recording. This form of optical disc was a very early form of the DVD U.S. Patent 3,430,966. It is of special interest that U.S. Patent 4,893,297, filed 1989, issued 1990, generated royalty income for Pioneer Corporation's DVA until 2007 —then encompassing the CD, DVD, and Blu-ray systems. In the early 1960s, the Music Corporation of America bought Gregg's patents and his company, Gauss Electrophysics.

Later, in the Netherlands in 1969, Philips Research physicists began their first optical videodisc experiments at Eindhoven. In 1975, Philips and MCA began to work together, and in 1978, commercially much too late, they presented their long-awaited Laserdisc in Atlanta. MCA delivered the discs and Philips the players. However, the presentation was a technical and commercial failure and the Philips/MCA cooperation ended.

In Japan and the U.S., Pioneer succeeded with the videodisc until the advent of the DVD. In 1979, Philips and Sony, in consortium, successfully developed the audio compact disc.

In the mid-1990s, a consortium of manufacturers developed the second generation of the optical disc, the DVD.

Magnetic disks found limited applications in storing the data in large amount. So,there was the need of finding some more data storing techniques. As a result, it was found that by using optical means large data storing devices can be made which in turn gave rise to the optical discs.The very first application of this kind was the Compact Disc(CD) which was used in audio systems.

 Sony and Philips developed the first generation of the CDs in the mid 1980s with the complete specifications for these clevices.With the help of this kind of technology the possibility of representing the analog signal into digital signal was exploited to great level.For this purpose the 16 bit samples of the analog signal were taken at the rate of 44,100 samples per second*hich was obviously following the Nyquist Criteria .The design of first version of the CD's was to hold up to 75 minutes of music which  was requiring 3GB of storage.

 The third generation optical disc was developed in 2000-2006, and was introduced as Blu-ray Disc. First movies on Blu-ray Discs were released in June 2006. Blu-ray eventually prevailed in a high definition optical disc format war over a competing format, the HD DVD. A standard Blu-ray disc can hold about 25 GB of data, a DVD about 4.7 GB, and a CD about 700 MB.

First-generation

Initially, optical discs were used to store music and computer software. The Laserdisc format stored analog video signals for the distribution of home video, but commercially lost to the VHS videocassette format, due mainly to its high cost and non-re-recordability; other first-generation disc formats were designed only to store digital data and were not initially capable of use as a digital video medium.

 Most first-generation disc devices had an infrared laser reading head. The minimum size of the laser spot is proportional to the wavelengthof the laser, so wavelength is a limiting factor upon the amount of information that can be stored in a given physical area on the disc. The infrared range is beyond the long-wavelength end of the visible light spectrum, so it supports less density than shorter-wavelength visible light. One example of high-density data storage capacity, achieved with an infrared laser, is 700 MB of net user data for a 12 cm compact disc.

Other factors that affect data storage density include: the existence of multiple layers of data on the disc, the method of rotation (Constant linear velocity (CLV), Constant angular velocity (CAV), or zoned-CAV), the composition of lands and pits, and how much margin is unused is at the center and the edge of the disc.

·         Compact Disc (CD) and derivatives

• Video CD (VCD)

• Super Video CD

        • Laserdisc

        • GD-ROM

        • Phase-change Dual

        • Double Density Compact Disc (DDCD)

        • Magneto-optical disc

·         MiniDisc

Second-generation

Second-generation optical discs were for storing great amounts of data, including broadcast-quality digital video. Such discs usually are read with a visible-light laser (usually red); the shorter wavelength and greater numerical aperture allow a narrower light beam, permitting smaller pits and lands in the disc. In the DVD format, this allows 4.7 GB storage on a standard 12 cm, single-sided, single-layer disc; alternatively, smaller media, such as the DataPlay format, can have capacity comparable to that of the larger, standard compact 12 cm disc.

·         DVD and derivatives

 • DVD-Audio

 • DualDisc

 • Digital Video Express (DIVX)

        • Nintendo optical disc

        • Super Audio CD

        • Enhanced Versatile Disc

        • Data Play

·         Universal Media Disc

·         Ultra Density Optical

Third-generation

 Third-generation optical discs are in development, meant for distributing high-definition video and support greater data storage capacities, accomplished with short-wavelength visible-light lasers and greater numerical apertures. Blu-ray Disc and HD DVD uses blue-violet lasers and focusing optics of greater aperture, for use with discs with smaller pits and lands, thereby greater data storage capacity per layer. In practice, the effective multimedia presentation capacity is improved with enhanced video data compression codecs such as H.264/MFEG-4 AVC and VC-1.

 • Biu-ray Disc (up to 128 GB (quad-layer))

• HD DVD (discontinued disc format, up to 51GB triple layer)

• CBHD (a derivative of the discontinued disc format HD DVD)

• Digital Multilayer Disk

 • Fluorescent Multilayer Disc

• Forward Versatile Disc

Fourth-generation

 The following formats go beyond the current third-generation discs and have the potential to hold more than one terabyte (1 T8) of data:

• Holographic Versatile Disc

 • LS-R

 • Protein-coated disc

Recordable and writable optical discs

There are numerous formats of optical direct to disk recording devices on the market, all of which are based on using a laser to change the reflectivity of the digital recording medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed. All formats enable reading of computer files as many times as desired by the user, but writing is a different situation. Some formats such as CD-R enable writes to be made only once to each sector on the disk, while other formats CD-RW enable multiple writes to the same sector which is more like a magnetic recording hard disk drive (HDD). In August 2011, a company named Millenniata announced a format called the M-DISC which, reverting to the original technology of optical disks, creates physical pits in a rock-like layer. The M-Disk is stable up to 500 °C (932 °F), is impervious to humidity issues, and is engineered to maintain its integrity for 1,000 years without degradation.

Specifications

Base (1x) and (current) maximum speeds by generation

Generation                                         Base                                                     Max

(Mbit/s)                               (Mbitls)               x

1st (CD)                                                1.17                                          65.6                      56x

2nd (DVD)                                           10.57                                    253.6                    24x

 3rd (BD)                                              36                                           504                        14x

Capacity and nomenclature

Designation                        Sides                    Layers (total)                    Diameter             Capacity

     (cm)                  (GB)       (GiB)

 BD                         SS SL            1                                        1                                    8                   7,8

BD                          SS DL          1                                        2                                     8                      15,6

 BD                         SS SL            1                                        1                                   12                     25

 BD                         SS DL          1                                        2                                   12                     50

 BD                         SS TL           1                                        3                                   12                     100

Magnetic storage

Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads. As of 2011, magnetic storage media, prirnarily hard disks, are widely used to store computer data as well as audio and video signals. ln the field of computing, the term magnetic storage is preferred and in the field of audio and video production, the term magnetic recording is more commonly used. The distinction is less technical and more a matter of preference. Other examples of magnetic storage media include floppy disks, magneticrecording tape, and magnetic stripes on credit cards.

History

Magnetic storage in the form of audio recording on a wire was publicized by Oberlin Smith in 1888. He filed a patent in September, 1878 but did not pursue the idea as his business was machine tools. The first publicly demonstrated (Paris Exposition of 1900) magnetic recorder was invented by Valdemar Poulsen in 1898. Poulsen's device recorded a signal on a wire wrapped around a drum. ln 1928, Fritz Pfleumer developed the first magnetic tape recorder. Early magnetic storage devices were designed to record analog audio signals. Computer and now most audio and video magnetic storage devices record digital data.

In old computers, magnetic storage was also used for primary storage in a form of magnetic drum, or core memory, core rope memory, thin film memory, twistor memory or bubble memory. Unlike modern computers, magnetic tape was also often used for secondary storage.

Design

Information is written to and read from the storage medium as it moves past devices called read-and-write heads that operate very close (often tens of nanometers) over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it.

 The magnetic surface is conceptually divided into many small sub-micrometer-sized magnetic regions, referred to as magnetic domains, (although these are not magnetic domains in a rigorous physical sense), each of which has a mosfly uniform magnetization. Due to the polycrystalline nature of the magnetic material each of these magnetic regions is composed of a few hundred magnetic grains. Magnetic grains are typically 10 nm in size and each form a single true magnetic domain. Each magnetic region in total forms a magnetic dipole which generates a magnetic field. ln older hard disk drive (HDD) designs the regions were oriented horizontally and parallel to the disk surface, but beginning about 2005, the orientation was changed to perpendicular to allow for closer magnetic domain spacing.

 For rellable storage of data, the recording material needs to resist self-demagnetization, which occurs when the magnetic dornains repel each other. Magnetic domains vvritten too densely together to a weakly magnetizable material will degrade over time due to rotation of the magnetic moment one or more domains to cancel out these forces. The domains rotate sideways to a halfway position that weakens the readability of the domain and relieves the magnetic stresses. Older hard disk drives used iron(111) oxide as the magnetic material, but current disks use a cobalt-based alloy.

A write head magnetizes a region by generating a strong local magnetic field, and a read head detects the magnetization of the regions. Early HDDs used an electromagnet both to magnetize the region and to then read its magnetic field by using electromagnetic induction. Later versions of inductive heads included metal in Gap (M1G) heads and thin film heads. As data density increased, read heads using magnetoresistance (MR) came into use; the electrical resistance of the head changed according to the strength of the magnetism from the platter. later development made use of spintronics; in read heads, the magnetoresistive effect was much greater than in earlier types, and was dubbed "glant" magnetoresistance (GMR). 1n today's heads, the read and write elements are separate, but in close proximity, on the head portion of an actuator arm. The read element is typically magneto-resistive while the write element is typically thin-film inductive.

The heads are kept from contacting the platter surface by the air that is extremely close to the platter; that air moves at or near the platter speed. The record and playback head are mounted on a block called a slider, and the surface next to the platter is shaped to keep it just barely out of contact. This forms a type of air bearing.

 Magnetic recording classes

Analog recording

Analog recording is based on the fact that remnant magnetization of a given material depends on the magnitude of the applied field. The magnetic material is normally in the form of tape, with the tape in its blank form being initially demagnetized. When recording, the tape runs at a constant speed. The writing head magnetizes the tape with current proportional to the signal. A magnetization distribution is achieved along the magnetic tape. Finally, the distribution of the magnetization can be read out, reproducing the original signal The magnetic tape is typically made by embedding magnetic particles in a plastic binder on polyester film tape. The commonly used magnetic particles are Iron oxide particles or Chromium oxide and metal particles with size of 0.5 micrometers.131 Analog recording was very popular in audio and video recording. ln the past 20 years, however, tape recording has been gradually replaced by digital recording.

 Digitai recording

Instead of creating a magnetization distribution in analog recording, digital recording only needs two stable magnetic states, which are the +Ms and -Ms on the hysteresis loop. Examples of digital recording are floppy disks and HDDs.

 Magneto-optical recording

Magneto-optical recording writes/reads optically. When writing, the magnetic medium is heated locally by a laser, which induces a rapid decrease of coercive field. Then, a small magnetic fieid can be used to switch the magnetization. The reading process is based on magneto-optical Kerr effect. The magnetic medium are typically amorphous R-FeCo thin film (R being a rare earth element). Magneto-optical recording is not very popular. One famous example is Minidisc developed by Sony.

Domain propagahon memory

 Domain propagation memory is also called bubble memory. The basic idea is to control domain wall motion in a magnetic medium that is free of microstructure. Bubble refers to a stable cylindrical domain. Data is then recorded by the presence/absence of a bubble domain. Domain propagation memory has high insensitivity to shock and vibration, so its application is usually in space and aeronautics.

Technical details

Access method

Magnetic storage media can be classified as either sequential access memory or random or serial access memory although in some cases the distinction is not perfectly clear. The access time can be defined as the average time needed to gain access to stored records. ln the case of magnetic wire, the read/write head only covers a very small part of the recording surface at any given time. Accessing different parts of the wire involves winding the wire forward or backward until the point of interest is found. The time to access this point depends on how far away it is from the starting point. The case of ferrite-core memory is the opposite. Every core location is immediate/y accessible at any given time.

Hard disks and modem linear serpentine tape drives do not precisely fit into either category. Both have many paraliel tracks across the width of the media and the read/write heads take time to switch between tracks and to scan within tracks. Different spots on the storage media take different amounts of time to access. For a hard disk this time is typically less than 10 ms, but tapes might take as much as 100 s.

Current usage

As of 2011, common uses of magnetic storage media are for c,omputer data mass storage on hard disks and the recording of analog audio and video works on analog tape. Since much of audio and video production is moving to digital systems, the usage of hard disks is expected to increase at the expense of analog tape. Digital tape and tape libraries are popular for the high capacity data storage of archives and backups. Floppy disks see some marginal usage, particularly in dealing with older computer systems and software. Magnetic storage is also widely used in some specific applications, such as bank cheques (MICR) and creditidebit cards (mag stripes).

 Future

A new type of magnetic storage, called Magnetoresistive Random Access Memory or MRAM, is being produced that stores data in magnetic bits based on the tunnel magnetoresistance (TMR) effect. Its advantage is non-volatility, low power usage, and good shock robustness. The ist generation that was developed was produced by Everspin Technologies, and utilized field induced writing. The 2nd generation is being developed through two approaches: Thermal Assisted Switching (TAS) which is currently being developed by Crocus Technology, and Spin Torque Transfer(STT) on which Crocus, Hynix, IBM, and several other companies are working. However, with storage density and capacity orders of magnitude smaller than an HDD, MRAM is useful in applications where moderate amounts of storage with a need for very frequent updates are required, which flash memory cannot support due to its limited write endurance.

Part  2

“basic software”

OPERATION SYSTEM

An operating system (0S) is a collection of software that manages computer hardware resources and provides common services for computer programs. The operating system is a vital component of the system software in a computer system. Application programs usually require an operating system to function.

Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting for cost allocation of processor time, mass storage, printing, and other resources.

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and will frequently make a system call to an OS function or be interrupted by it. Operating systerns can be found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.

Examples of popular modern operating systems include Androld, BSD, i0S, Linux, Mac OS X, Microsoft Windows, Windows Phone, and IBM z/OS. All these, except Windows and z/OS, share roots in UNIX.

Types of operating systems

 Real-time

 A real-time operating system is a multitasking operating system that aims at executing real-time applications. Real-time operating systems often use specialized scheduling algorithms so that they can achieve a deterministic nature of behavior. The main objective of real-time operating systems is their quick and predictable response to events. They have an event-driven or time-sharing design and often aspects of both. An event-driven systern switehes between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock interrupts.

Multi-user

A multi-user operating system allows multiple users to access a computer system at the same time. Time-sharing systems and Internet servers can be classified as multi-user systems as they enable multiple-user access to a computer through the sharing of time. Single-user operating systems have only one user but may aliow multiple programs to run at the same time.

Multi-tasking vs. singie-tasking

 A multi-tasking operating system allows more than one prograrn to be running at a time, from the point of view of human time scales. A single-tasking system has only one running program. Multi-tasking can be of two types: pre-emptive and co-operative. ln pre-emptive multitasking, the operating system slices the CPU time and dedicates one slot to each of the programs. operating systems such as Solaris and Linux support pre-emptive muititasking, as does Amiga0S. Cooperative multitasking is achieved by relying on each process to give time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking. 32-bit versions of both Windows NT and Win9x, used pre-emptive multi-tasking. Mac OS prior to OS X used to support cooperative multitasking.

Distributed

A distributed operating system manages a group of independent computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing. Distributed computations are carried out on more than one machine. When computers in a group work in cooperation, they make a distributed system.

Embedded

Ennbedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy. They are able to operate with a limited number of resources. They are very compact and extremely efficient by design. Windows CE and Minix 3 are some examples of embedded operating systems.

 History

 Early computers were bullt to perform a series of single tasks, like a calculator. Operating systems did not exist in their modern and more complex forms until the early 1960s. Basic operating system features were developed in the 1950s, such as resident monitor funetions that could automatically run different programs in succession to speed up processing. Hardware features were added that enabled use of runtime libraries, interrupts, and parallel processing. When personal computers became popular in the 1980s, operating system were made for them similar in concept to those used on larger computers.

 In the 1940s, the earliest electronic digital systems had no operating systems. Electronic systems of this time were programmed on rows of mechanical switches or by jumper wires on plug boards. These were special-purpose systems that, for example, generated ballistics tables for the military or controlled the printing of payroll checks from data on punched paper cards. After programrnable general purpose computers were invented, machine languages (consisting of strings of the binary digits 0 and 1 on punched paper tape) were introduced that sped up the programming process (Stern, 1981).

In the early 1950s, a computer could execute only one program at a time. Each user had sole use of the computer for a limited period of time and would arrive at a scheduled time with program and data on punched paper cards and/or punched tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a front panel using toggle switches and panel lights. lt is said that Aian Turing was a master of this on the early Manchester Mark 1 machine, and he was already deriving the primitive conception of an operating system from the principles of the Universal Turing machine.

Later machines came with libraries of programs, which would be linked to a user's program to assist in operations such as input and output and generating computer code from human-readable syrnbolic code. This was the genesis of the modern-day computer system. However, machines still ran a single job at a time. At Cambridge University in England the job queue was at one time a washing line from which tapes were hung with different colored clothes-pegs to indicate job-priority.

Exampies of operating systems

 UNIX and unix-like operating systems

 Unix was originally written in assembly language. Ken Thompson wrote B, mainly based on BCPL, based on his experience in the MULTICSproject. B was replaced by C, and Unix, rewriten in C, developed into a large, complex family of inter-related operating systems which have been influential in every modern operating system (see History).

The UNIX-Iike family is a diverse group of operating systems, with several major sub-categories including System V, BSD, and Linux. The name "UNIX" is a trademark of The Open Group which licenses it for use with any operating system that has been shown to conform to their definitions. "UNIX-like"is commonly used to refer to the large set of operating systems which resemble the original UNIX.

 Unix-like systems run on a wide varlety of computer architectures. They are used heavily for servers in business, as well as workstations in academic and engineering environments. Free UNIX variants, such as Linux and BSD, are popular in these areas.

Four operating systems are certified by the The Open Group (holder of the Unix trademark) as Unix. HP's HP-UX and IBM's AIX are both descendants of the original System V Unix and are designed to run only on their respective vendor's hardware. In contrast, Sun Microsystems'sSolaris Operating System can run on multiple types of hardware, including x86 and Sparc servers, and PCs. Apple's Mac OS X, a replacement for Appie's earlier (non-Unix) Mac OS, is a hybrid kernel-based BSO variant derived from NeXTSTEP, Mach, and FreeBSD.

Unix interoperability was sought by establishing the POS1X standard. The POSIX standard can be applied to any operating system, although it was originally created for various Unix variants.

Microsoft Windows

Microsoft Windows is a family of proprietary operating systems designed by Microsoft Corporation and primarily targeted to Intel architecture based computers, with an estimated 88.9 percent total usage share on Web connected computers. The newest version is Windows 8 for workstations and Windows Server 2012 for servers. Windows 7 recently overtook Windows XP as most used OS.

Microsoft Windows originated in 1985 as a operating environment running on top of MS-DOS, which was the standard operating system shipped on most Intel architecture personal computers at the time. ln 1995, Windows 95 was released which only used MS-DOS as a bootstrap. For backwards compatibility, Win9x could run real-mode MS-DOS and 16 bits Windows 3.x drivers. Windows Me, released in 2000, was the last version in the Win9x family. Later versions have all been based on the Windows NT kernel. Current versions of Windows run on 1A-32 and x86-64microprocessors, aithough Windows 8 wiii support ARM architecture. In the past, Windows NT supported non-intel architectures.

Server editions of Windows are widely used. in recent years, Microsoft has expended significant capital in an effort to promote the use of Windows as a server operating system. However, Windows usage on servers is not as widespread as on personal computers, as Windows competes against Linux and BSD for server market share.

Other

There have been many operating systems that were significant in their day but are no longer so, such as Amiga0S; OS/2 from IBM and Microsoft;Mac OS, the non-Unix precursor to Apple's Mac OS X; Be0S; XTS-300; RISC OS; MorphOS and FreeMint. Sorne are still used in niche markets and continue to be developed as minority platforms for enthusiast communities and specialist applications. OpenVMS formerly from DEC, is still under active development by Hewlett-Packard. Yet other operating systems are used almost exclusively in academia, for operating systems education or to do research on operating system concepts. A typical example of a system that fulfills both roles is MINIX, while for exampleSingularity is used purely for research.

 Other operating systems have falled to win significant market share, but have introduced innovations that have influenced mainstream operating systems, not least Bell Labs' Plan 9.

Components

 The components of an operating system all exist in order to make the different parts of a computer work together. All user software needs to go through the operating system in order to use any of the hardware, whether it be as simple as a mouse or keyboard or as complex as an Internet component.

Kernel

With the aid of the firmware and device drivers, the kernel provides the most basic level of control over all of the computer's hardware devices. It manages memory access for programs in the RAM, it determines which programs get access to which hardware resources, it sets up or resets the CPU's operating states for optimal operation at all times, and it organizes the data for long-term non-volatile storage with file systems on such media as disks, tapes, flash memory, etc.

 Networking

 Currently most operating systems support a variety of networking protocols, hardware, and applications for using them. This means that computers running dissimilar operating systems can participate in a common network for sharing resources such as computing, files, printers, and scanners using either wired or wireless connections. Networks can essentially allow a computer's operating system to access the resources of a remote computer to support the same functions as it could if those resources were connected directly to the local computer. This includes everything from simple communication, to using networked file systems or even sharing another computer's graphics or sound hardware. Some network services allow the resources of a computer to be accessed transparently, such as SSH which allows networked users direct access to a computer's command line interface.

 Client/server networking allows a program on a computer, called a client, to connect via a network to another computer, called a server. Servers offer (or host) various services to other network computers and users. These services are usually provided through ports or numbered access points beyond the server's network address. Each port number is usually associated with a maximum of one running program, which is responsible for handling requests to that port. A daemon, being a user program, can in turn access the local hardware resources of that computer by passing requests to the operating system kernel.

Many operating systems support one or more vendor-specific or open networking protocols as well, for example, SNA on IBM systems, DECnet on systems from Digital Equipment Corporation, and Microsoft-specific protocols (SMB) on Windows. Specific protocols for specific tasks may atso be supported such as NFS for file access. Protocols like ESound, or esd can be easily extended over the network to provide sound from local applications, on a remote system's sound hardware.

Security

A computer being secure depends on a number of technologies working properly. A modern operating system provides access to a number of resources, which are available to software running on the system, and to external devices like networks via the kernel.

The operating systern must be capable of distinguishing between requests which should be allowed to be processed, and others which should not be processed. While some systems may simply distinguish between "privileged" and "non-privileged", systems commonly have a form of requester identity, such as a user name. To establish identity there may be a process of authentication. Often a username must be quoted, and each username may have a password. Other methods of authentication, such as magnetic cards or biometric data, might be used instead. In some cases, especially connections from the network, resources may be accessed with no authentication at all (such as reading files over a network share). Also covered by the concept of requester identityis authorization; the particular services and resources accessible by the requester once logged into a system are tied to either the requester's user account or to the variously configured groups of users to which the requester belongs.

In addition to the allow/disallow model of security, a system with a high level of security will also offer auditing options. These would allow tracking of requests for access to resources (such as, "who has been reading this file?"). Internal security, or security from an already running program is onIy possible if all

possibly harmful requests must be carried out through interrupts to the operating system kernel. If programs can directly access hardware and resources, they cannot be secured.

External security involves a request from outside the computer, such as a login at a connected console or some kind of network connection. External requests are often passed through device drivers to the operating system's kernel, where they can be passed onto applications, or carried out directly. Security of operating systems has long been a concern because of highly sensitive data held on computers, both of a commercial and military nature. The United States Government Department of Defense (DoD) created the Trusted Computer System Evaluation Criteria (TCSEC) which is a standard that sets basic requirements for assessing the effectiveness of security. This became of vital importance to operating system makers, because the TCSEC was used to evaluate, classify and select trusted operating systems being considered for the processing, storage and retrieval of sensitive or classified information.

Network services include offerings such as file sharing, print services, email, web sites, and file transfer protocols (FTP), most of which can have compromised security. At the front line of security are hardware devices known as firewalls or intrusion detection/prevention systems. At the operating system level, there are a number of software firewalis available, as well as intrusion detection/prevention systems. Most modern operating systems include a software firewall, which is enabled by default. A software firewall can be configured to allow or deny network traffic to or from a service or application running on the operating system. Therefore, one can install and be running an insecure service, such as Telnet or FTP, and not have to be threatened by a security breach because the firewall would deny all traffic trying to connect to the service on that port.

An alternative strategy, and the only sandbox strategy available in systems that do not meet the Popek and Goldberg virtualization requirements, is the operating system not running user programs as native code, but instead either emulates a processor or provides a host for a p-code based system such as Java.

Internal security is especially relevant for multi-user systems; it allows each user of the system to have private files that the other users cannot tamper with or read. Internal security is also vital if auditing is to be of any use, since a program can potentially bypass the operating system, inclusive of bypassing auditing.

FACE OF INTERNET

The Internet (or Internet) is a global system of interconnected computer networks that use the standard Internet protocol suite (often called TCP/IP, although not all applications use TCP) to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents of the World Wide Web (WWW) and the infrastructure to support email.

Most traditional communications media including telephone, music, film, and television are being reshaped or redefined by the Internet, giving birth to new services such as Voice over Internet

Protocol (VolP) and Internet Protocol Television (IPIV). Newspaper, book and other print publishing are adapting toWeb site technology, or are reshaped into blogging and web feeds. The Internet has enabled and accelerated new forms of human interactions throughinstant messaging, Internet forums, and social networking. Online shopping has boomed both for major retail outlets and small artisans and traders. Business-to-business and financial services on the Internet affect supply chains across entire Industries.

The origins of the Internet reach back to research of the 1960s, commissioned by the United States government to build robust, fault-tolerant, and distributed computer networks. The funding of a new U.S. backbone by the National Science Foundation in the 1980s, as well as private funding for other commercial backbones, led to worldwide participation in the development of new networking technologies, and the merger of many networks. Thecommercialization of what was by the 1990s an international network resulted in its popularization and incorporation into virtually every aspect of modern human life. As of June 2012, more than 2.4 billion people—nearly a third of the world's human population—have used the services of the Internet.

The Internet has no centralized governance in either technological implementation or policies for access and usage; each constituent network sets its own standards. Only the overreaching definitions of the two principal name spaces in the Internet, the Internet Protocol address space and the Domain Name System, are directed by a maintainer organization, the Internet Corporation for Assigned Names and Numbers (ICANN). The technical underpinning and standardization of the core protocols (IPv4 and IPv6) is an activity of the Internet Engineering Task Force (IETF), a non-profit organization of loosely affiliated international participants that anyone may associate with by contributing technical expertise.

History

Research into packet switching started in the early 1960s and packet switched networks such as Mark I at NPL in the UK, ARPANET, CYCLADES, Merit Network, Tymnet, and Telenet, were developed in the late 1960s and early 1970s using a variety of protocols. The ARPANET in particular led to the development of protocols for internetworking, where multiple separate networks could be joined together into a network of networks thanks to the work of Britishscientist Donald Davies whose ground-breaking work on Packet Switching was essential to the system.

The first two nodes of what would become the ARPANET were interconnected between Leonard Kleinrock's Network Measurement Center at the UCLA's School of Engineering and Applied Science and Douglas Engelbart's NLS system at SRI International (SRI) in Menlo Park, California, on 29 October 1969. The third site on the ARPANET was the Culler-Fried Interactive Mathematics center at the University of California at Santa Barbara, and the fourth was the University of Utah Graphics Department. In an early sign of future growth, there were already fifteen sites connected to the young ARPANET by the end of 1971. These early years were documented in the 1972 film Computer Networks: The Heralds of Resource Sharing.

Early international collaborations on ARPANET were sparse. For various political reasons, European developers were concerned with developing the X.25networks. Notable exceptions were the Norwegian Seismic Array (NORSAR) in June 1973, followed in 1973 by Sweden with satellite links to the TanumEarth Station and Peter T. Kirstein's research group in the UK, initially at the Institute of Computer Science, University of London and later at University College London.

In December 1974, RFC 675– Specification of Internet Transmission Control Program, by Vinton Cerf, Yogen Dalai, and Carl Sunshine, used the term internet, as a shorthand for internetworking;

later RFCs repeat this use, so the word started out as an adjectiverather than the noun it is today. Access to the ARPANET was expanded in 1981 when the National Science Foundation (NSF) developed theComputer Science Network (CSNET). In 1982, the Internet Protocol Suite (TCP/IP) was standardized and the concept of a world-wide network of fully interconnected TCP/IP networks called the Internet was introduced.

TCP/IP network access expanded again in 1986 when the National Science Foundation Network (NSFNET) provided access to supercomputer sites in the United States from research and education organizations, first at 56 kbit/s and later at 1.5 Mbit/s and 45 Mbit/s. Commercial interne service providers (ISPs) began to emerge in the late 1980s and early 1990s. The ARPANET was decommissioned in 1990. The Internet was commercialized in 1995 when NSFNET was decommissioned, removing the last restrictions on the use of the Internet to carry commercial traffic. The Internet started a rapid expansion to Europe and Australia in the mid to late 1980s and to Asia in the late 1980s and early 1990s.

Since the mid-1990s the Internet has had a tremendous impact on culture and commerce, including the rise of near instant communication by email,instant messaging, Voice over Internet Protocol (VolP) "phone calls", two-way interactive video calls, and the World Wide Web with its discussion forums, blogs, social networking, and online shopping sites. Increasing amounts of data are transmitted at higher and higher speeds over fiber optic networks operating at 1-Gbit/s, 10-Gbit/s, or more. The Internet continues to grow, driven by ever greater amounts of online information and knowledge, commerce, entertainment and social networking.

During the late 1990s, it was estimated that traffic on the public Internet grew by 100 percent per year, while the mean annual growth in the number of Internet users was thought to be between 20% and 50%. This growth is often attributed to the lack of central administration, which allows organic growth of the network, as well as the non-proprietary open nature of the Internet protocols, which encourages vendor interoperability and prevents any one company from exerting too much control over the network. As of 31 March 2011, the estimated total number of Internet users was 2.095 billion (30.2% of world population). It is estimated that in 1993 the Internet carried only 1% of the information flowing through two-way telecommunication, by 2000 this figure had grown to 51%, and by 2007 more than 97% of all telecommunicated information was carried over the Internet.

Technology

Protocols

The communications infrastructure of the Internet consists of its hardware components and a system of software layers that control various aspects of the architecture. While the hardware can often be used to support other software systems, it is the design and the rigorous standardization process of the software architecture that characterizes the Internet and provides the foundation for its scalability and success. The responsibility for the architectural design of the Internet software systems has been delegated to the Internet Engineering Task Force (IETF), The IETF conducts standard-setting work groups, open to any individual, about the various aspects of Internet architecture. Resulting discussions and final standards are published in a series of publications, each called a Request for Comments (RFC), freely available on the IETF web site. The principal methods of networking that enable the Internet are contained in specially designated RFCs that constitute the Internet Standards. Other less rigorous documents are simply informative, experimental, or historical, or document the best current practices (BCP) when implementing Internet technologies.

The Internet standards describe a framework known as the Internet protocol suite. This is a model architecture that divides methods into a layered system of protocols (RFC 1122, RFC 1123). The layers correspond to the environment or scope in which their services operate. At the top is the application layer, the space for the application-specific networking methods used in software applications, e.g., a web browser program. Below this top layer, the transport layer connects applications on different hosts via the network (e.g., client—server model) with appropriate data exchange methods. Underlying these layers are the core networking technologies, consisting of two layers. The internet layer enables computers to identify and locate each other via Internet Protocol (IP) addresses, and allows them to connect to one another via intermediate (transit) networks. Last, at the bottom of the architecture, is a software layer, the link layer, that provides connectivity between hosts on the same local network link, such as a local area network (LAN) or a dial-up connection. The model, also known as TCP/IP, is designed to be independent of the underlying hardware, which the model therefore does not concern itself with in any detail. Other models have been developed, such as the Open Systems Interconnection (051) model, but they are not compatible in the details of description or implementation; many similarities exist and the TCP/IP protocols are usually included in the discussion of OS! networking.

The most prominent component of the Internet model is the Internet Protocol (IF'), which provides addressing systems (lP addresses) for computers on the Internet. IP enables internetworking and in essence establishes the Internet itself. IF' Version 4 (IPv4) is the initial version used on the first generation of today's Internet and is still in dominant use. It was designed to address up to ^—4.3 billion (10⁹) Internet hosts. However, the explosive growth of the Internet has led to IPv4 address exhaustion, which entered its final stage in 2011, when the global address allocation pool was exhausted. A new protocol version, IPv6, was developed in the mid-1990s, which provides vastly larger addressing capabilities and more efficient routing of Internet traffic. IPv6 is currently in growing deployment around the world, since Internet address registries (RIRs) began to urge all resource managers to plan rapid adoption and conversion.

1Pv6 is not interoperable with IPv4. in essence, it establishes a parallel version of the Internet not directly accessible with IPv4 software. This means software upgrades or translator facilities are necessary for networking devices that need to communicate on both networks. Most modern computer operating systems already support both versions of the Internet Protocol. Network infrastructures, however, are still lagging in this development. Aside from the complex array of physical connections that make up its infrastructure, the Internet is facilitated by bi- or multi-lateral commercial contracts (e.g., peering agreements), and by technical specifications or protocols that describe how to exchange data over the network. Indeed, the Internet is defined by its interconnections and routing policies.

Routing

Internet Service Providers connect customers (thought of at the "bottom" of the routing hierarchy) to customers of other ISPs. At the "top" of the routing hierarchy are ten or so Tier 1 networks, large telecommunication companies which exchange traffic directly "across" to all other Tier 1 networks via unpaid peering agreements. Tier 2 networks buy Internet transit from other ISP to reach at least some parties on the global Internet, though they may also engage in unpaid peering (especially for local partners of a similar size).1SPs can use a single "upstream" provider for connectivity, or use multihoming to provide protection from problems with individual links. Internet exchange points create physical connections between multiple ISPs, often hosted in buildings owned by independent third parties.

Computers and routers use routing tables to direct IF' packets among locally connected machines. Tables can be constructed manually or automatically via DHCP for an individual computer or a routing protocol for routers themselves. In single-homed situations, a default route usually points "up" toward an ISP providing transit. Higher-level ISPs use theBorder Gateway Protocol to sort out paths to any given range of IP addresses across the complex connections of the global Internet.

Academic institutions, large companies, governments, and other organizations can perform the same role as 1SPs, engaging in peering and purchasing transit on behalf of their internal networks of individual computers. Research networks tend to interconnect into large subnetworks such

as GEANT, GLORIA), Internet2, and the UK's national research and education network, JANET. These in turn are built around smaller networks.

Not all computer networks are connected to the Internet. For example, some classified United States websites are only accessible from separate secure networks.

General structure

The Internet structure and its usage characteristics have been studied extensively. It has been determined that both the Internet IP routing structure and hypertext links of the World Wide Web are examples of scale-free networks.

Many computer scientists describe the Internet as a "prime example of a large-scale, highly engineered, yet highly complex system". The Internet is heterogeneous; for instance, data transfer rates and physical characteristics of connections vary widely. The Internet exhibits "emergent phenomena" that depend on its large-scale organization. For example, data transfer rates exhibit temporal self-similarity. The principles of the routing and addressing methods for traffic in the Internet reach back to their origins in the 1960s when the eventual scale and popularity of the network could not be anticipated. Thus, the possibility of developing alternative structures is investigated.¹³³¹The Internet structure was found to be highly robust to random failures and very vulnerable to high degree attacks.

Services

World Wide Web

Many people use the terms Internet and World Wide Web, or Just the Web, Interchangeably, but the two terms are not synonymous. The World Wide Web is a global set of documents, imagesand other resources, logically interrelated by hyperlinks and referenced with Uniform Resource Identifiers (URIs). URls symbolically identify services, servers, and other databases, and the documents and resources that they can provide. Hypertext Transfer Protocol (HTTP) is the main access protocol of the World Wide Web, but it is only one of the hundreds of communication protocols used on the Internet. Web services also use HTTP to allow software systems to communicate in order to share and exchange business logic and data.

World Wide Web browser software, such as Microsoft's Internet Explorer, Mozilla Firefox, Opera, Apple's Safari, and Google Chrome, lets users navigate from one web page to another via hyperlinks embedded in the documents. These documents may also contain any combination of computer data, including graphics, sounds, text, video, multimedia and interactive content that runs while the user is interacting with the page. Client-side software can include animations, games, office applications and scientific demonstrations. Through keyword-driven Internet researchusing search engines like Yahoo! and Google, users worldwide have easy, instant access to a vast and diverse amount of online information. Compared to printed media, books, encyclopedias and traditional libraries, the World Wide Web has enabled the decentralization of information on a large scale.

The Web has also enabled individuals and organizations to publish ideas and information to a potentially large audience online at greatly reduced expense and time delay. Publishing a web page, a blog, or building a website involves little initial cost and many cost-free services are available. Publishing and maintaining large, professional web sites with attractive, diverse and up-to-date information is still a difficult and expensive proposition, however. Many individuals and some companies and groups use web logs or blogs, which are largely used as easily updatable online diaries. Some commercial organizations encourage staff to communicate advice in their areas of specialization in the hope that visitors will be impressed by the expert knowledge and free information, and be attracted to the corporation as a result. One example of this practice is Microsoft, whose product developers publish their personal blogs in order to pique the public's interest in their work. Collections of personal web pages published by large service providers remain popular, and have become increasingly sophisticated. Whereas operations such as Angelfire andGeoCities have existed since the early days of the Web, newer offerings from, for example, Facebook and Twitter currently have large followings. These operations often brand themselves associal network services rather than simply as web page hosts.

Advertising on popular web pages can be lucrative, and e-commerce or the sale of products and services directly via the Web continues to grow.

When the Web began in the 1990s, a typical web page was stored in completed form on a web server, formatted in HTML, ready to be sent to a user's browser in response to a request. Over time, the process of creating and serving web pages has become more automated and more dynamic. Websites are often created using content management or wiki software with, initially, very little content. Contributors to these systems, who may be paid staff, members of a club or other organization or members of the public, fill underlying databases with content using editing pages designed for that purpose, while casual visitors view and read this content in its final HTML. form. There may or may not be editorial, approval and security systems built into the process of taking newly entered content and making it available to the target visitors.

 Communication

 Email is an important communications service available on the Internet. The concept of sending electronic text messages between parties in a way analogous to mailing letters or memos predates the creation of the Internet. Pictures, documents and other files are sent as email attachments. Emails can be cc-ed to multiple email addresses.

Internet telephony is another common communications service made possible by the creation of the Internet. VolP stands for Voice-over-Internet Protocol, referring to the protocol that underlies all Internet communication. The idea began in the early 1990s with walkie-talkie-like voice applications for personal computers. In recent years many VolP systems have become as easy to use and as convenient as a normal telephone. The benefit is that, as the Internet carries the voice traffic, VolP can be free or cost much less than a traditional telephone call, especially over long distances and especially for those with always-on Internet connections such as cable or ADSL. VolP is maturing into a competitive alternative to traditional telephone service. Interoperability between different providers has improved and the ability to call or receive a call from a traditional telephone is available. Simple, inexpensive VolP network adapters are available that eliminate the need for a personal computer.

 Voice quality can still vary from call to call, but is often equal to and can even exceed that of traditional calls. Remaining problems for VolP include emergency telephone number dialing and reliability. Currently, a few VolP providers provide an emergency service, but it is not universally available. Traditional phones are line-powered and operate during a power failure; VolP does not do so without a backup power source for the phone equipment and the Internet access devices. VoIP has also become increasingly popular for gaming applications, as a form of communication between players. Popular VolP clients for gaming include Ventrilo and Teamspeak. Wii, PlayStation 3, and )(box 360 also offer VolP chat features.

Data transfer

File sharing is an example of transferring large amounts of data across the Internet. A computer file can be emailed to customers, colleagues and friends as an attachment. It can be uploaded to a website or FrP server for easy download by others. It can be put into a "shared location" or onto a file server for instant use by colleagues. The load of bulk downloads to many users can be eased by the use of "mirror" servers or peer-to-peer networks. In any of these cases, access to the file may be controlled by user authentication, the transit of the file over the Internet may be obscured by encryption, and money may change hands for access to the file. The price can be paid by the remote charging of funds from, for example, a credit card whose details are also passed — usually fully encrypted — across the Internet. The origin and authenticity of the file received may be checked by digital signatures or by MD5 or other message digests. These simple features of the Internet, over a worldwide basis, are changing the production, sale, and distribution of anything that can be reduced to a computer file for transmission. This includes all manner of print publications, software products, news, music, film, video, photography, graphics and the other arts. This In turn has caused seismic shifts in each of the existing industries that previously controlled the production and distribution of these products.

 Streaming media is the real-time delivery of digital media for the immediate consumption or enjoyment by end users. Many radio and television broadcasters provide Internet feeds of their live audio and video productions. They may also allow time-shift viewing or listening such as Preview, Classic Clips and Listen Again features. These providers have been joined by a range of pure Internet "broadcasters" who never had on-air licenses. This means that an Internet-connected device, such as a computer or something more specific, can be used to access on-line media in much the same way as was previously possible only with a television or radio receiver. The range of available types of content is much wider, from specialized technical webcasts to on-demand popular multimedia services. Podcasting is a variation on this theme, where — usually audio — material is downloaded and played back on a computer or shifted to a portable media player to be listened to on the move. These techniques using simple equipment allow anybody, with little censorship or licensing control, to broadcast audio-visual material worldwide.

Digital media streaming increases the demand for network bandwidth. For example, standard image quality needs 1 Mbit/s link speed for SD 480p, HD 720p quality requires 2.5 Mbit/s, and the top-of-the-line HDX quality needs 4.5 Mbit/s for 1080p.

Webcams are a low-cost extension of this phenomenon. While some webcams can give full-frame-rate video, the picture either is usually small or updates slowly. Internet users can watch animals around an African waterhole, ships in the Panama Canal, traffic at a local roundabout or monitor their own premises, live and in real time. Video chat rooms and video conferencing are also popular with many uses being found for personal webcams, with and without two-way sound. YouTube was founded on 15 February 2005 and is now the leading website for free streaming video with a vast number of users. It uses a flash-based web player to stream and show video files. Registered users may upload an unlimited amount of video and build their own personal profile. YouTube claims that its users watch hundreds of millions, and upload hundreds of thousands of videos daily.

 Access

Common methods of Internet access in homes include dial-up, landline broadband (over coaxial cable, fiber optic or copper wires), Wi-Fi, satellite and 3G/4G technology cell phones. Public places to use the Internet include libraries and Internet cafes, where computers with Internet connections are available. There are also Internet access points in many public places such as airport halls and coffee shops, in some cases just for brief use while standing. Various terms are used, such as "public Internet kiosk", "public access terminal", and "Web payphone". Many hotels now also have public terminals, though these are usually fee-based. These terminals are widely accessed for various usage like ticket booking, bank deposit, online payment etc. Wi-Fi provides wireless access to computer networks, and therefore can do so to the Internet itself. Hotspots providing such access include Wi-Fl cafes, where would-be users need to bring their own wireless-enabled devices such as a laptop or PDA. These services may be free to all, free to customers only, or fee-based. A hotspot need not be limited to a confined location. A whole campus or park, or even an entire city can be enabled.

Grassroots efforts have led to wireless community networks. Commercial Wi-Fl services covering large city areas are in place in London, Vienna, Toronto, San Francisco, Philadelphia, Chicago and Pittsburgh. The Internet can then be accessed from such places as a park bench. Apart from Wi-Fi, there have been experiments with proprietary mobile wireless networks like Ricochet, various high-speed data services over cellular phone networks, and fixed wireless services. High-end mobile phones such as smartphones in general come with Internet access through the phone network. Web browsers such as Opera are availabie on these advanced handsets, which can also run a wide variety of other Internet software. More mobile phones have Internet access than PCs, though this is not as widely used. An Internet access provider and protocol matrix differentiates the methods used to get online.

An Internet blackout or outage can be caused by local signaling interruptions. Disruptions of submarine communications cables may cause blackouts or slowdowns to large areas, such as in the2008 submarine cable disruption. Less-developed countries are more vulnerable due to a small number of high-capacity links. Land cables are also vulnerable, as in 2011 when a woman digging for scrap nnetal severed most connectivity for the nation of Armenia. Intemet blackouts affecting almost entire countries can be achieved by governments as a form of Internet censorship, as in the blockage of the Internet in Egypt, whereby approximately 93% of networks were without access in 2011 in an attempt to stop mobilization for anti-government protests.

SPREEDSHETS

A spreadsheet is an interactive computer application program for organization and analysis of information in tabular form. Spreadsheets developed as computerized simulations of paper accounting worksheets. The program operates on data represented as cells of an array, organized in rows and columns. Each cell of the array is a model—view—controller element that can contain either numeric or text data, or the results of formulas that automatically calculate and display a value based on the contents of other cells.

The user of the spreadsheet can make changes in any stored value and obsen/e the effects on calculated values. This makes the spreadsheet useful for "what-if' analysis since many cases can be rapidly investigated without tedious manual recalculation. Modern spreadsheet software can have multiple interacting sheets, and can display data either as text and numerals, or in graphical form.

 In addition to the fundamental operations of arithmetic and mathematical functions, modern spreadsheets provide built-in functions for common financial and statistical operations. Such calculations as net present value or standard deviation can be applied to tabular data with a pre-programmed function in a formula. Spreadsheet programs also provide conditional expressions, functions to convert between text and numbers, and functions that operate on strings of text.

Spreadsheets have now replaced paper-based systems throughout the business world. Although they were first developed for accounting or bookkeeping tasks, they now are used extensively in any context where tabular lists are built, sorted, and shared.

Visicalc was the first electronic spreadsheet on a microcomputer, and it helped tum the Apple II computer into a popular and widely used system. Lotus 1-2-3 was the leading spreadsheet whenDOS was the dominant operating system. Excel now has the largest market share on the Windows and Macintosh platforms. A spreadsheet program is a standard feature of an office productivity suite; since the advent of web apps, office suites now also exist in web app form.

 Spreadsheet use

 A modern spreadsheet file consists of multiple worksheets (usually called by the shorter name sheets) that make up one workbook, with each file being one workbook. A cell on one sheet is capable of referencing cells on other, different sheets, whether within the same workbook or even, in some cases, in different workbooks.

Spreadsheets share many principles and traits of databases, but spreadsheets and databases are not the same thing. A spreadsheet is essentially just one table, whereas a database is a collection of many tables with machine-readable semantic relationships between them. While it is true that a workbook that contains three sheets is indeed a file containing multiple tables that can interact with each other, it lacks the relational structure of a database. Spreadsheets and databases are interoperable—sheets can be imported into databases to become tables within them, and database queries can be exported into spreadsheets for further analysis.

A spreadsheet program is one of the main components of an office productivity suite, which usually also contain aword processor, a presentation program, and a database management system. Programs within a suite use similar commands for similar functions. Usually sharing data between the components is easier than with a non-integrated collection of functionally equivalent programs. This was particularly an advantage at a time when many personal computer systems used text-mode displays and commands, instead of a graphical user interface.

 History

Paper spreadsheets

 The word "spreadsheet" came from "spread" in its sense of a newspaper or magazine item (text and/or graphics) that covers two facing pages, extending across the center fold and treating the two pages as one large one. The compound word "spread-sheet" came to mean the format used to present book-keeping ledgers—with columns for categories of expenditures across the top, invoices listed down the left margin, and the amount of each payment in the cell where its row and column intersect—which were, traditionally, a "spread" across facing pages of a bound ledger (book for keeping accounting records) or on oversized sheets of paper (termed "analysis paper") ruled into rows and columns in that format and approximately twice as wide as ordinary paper.

Lotus 1-2-3 and other MS-DOS spreadsheets

 The acceptance of the IBM PC following its introduction in August, 1981, began slowly, because most of the programs available for it were translations from other computer models. Things changed dramatically with the introduction of Lotus 1-2-3 in November, 1982, and release for sale in January, 1983. Since it was written especially for the IBM PC, it had good performanceand became the killer app for this PC. Lotus 1-2-3 drove sales of the PC due to the improvements in speed and graphics compared to VisiCalc on the Apple II. Lotus 1-2-3, along with its competitor Borland Quattro, soon displaced VisiCalc. Lotus 1-2-3 was released on January 26, 1983, started outselling then-most-popular VisiCalc the very same year, and for a number of years was the leading spreadsheet for DOS.

Microsoft Excel

Microsoft developed Excel on the Macintosh platform for several years, and then ported it to Windows 2.0. The Windows 3.x platforms of the early 1990s made it possible for Excel to take market share from Lotus. By the time Lotus responded with usable Windows products, Microsoft had begun to assemble their Office suite. Starting in the mid 1990s continuing through the present, Microsoft Excel has dominated the commercial electronic spreadsheet market.

 Open source software

 Gnumeric is a free, cross-platform spreadsheet program that is part of the GNOME Free Software Desktop Project. OpenOffice.org Calc and the very closely related LibreOffice Calc are free and open-source spreadsheets, also licensed under the GPL.

Web based spreadsheets

With the advent of advanced web technologies such as Ajax circa 2005, a new generation of online spreadsheets has emerged. Equipped with a rich Internet application user experience, the best web based online spreadsheets have many of the features seen in desktop spreadsheet applications. Some of them such as Office Web Apps or Google Spreadsheets also have strong multi-user collaboration features and / or offer real time updates from remote sources such as stock prices and currency exchange rates.

Other spreadsheets

A list of current spreadsheet software

·         IBM Lotus Symphony (2007)

      • Corel Quattro Pro (WordPerfect Office)

       • Kspread

        • Kingsoft Spreadsheets

        • Numbers is Apple Inc.'s spreadsheet software, part of iWork.

        • ZCubes-Calci

        • Resolver One

        • GNU Oleo — A traditional terminal mode spreadsheet for UNIX/UNIX-like systems

 Concepts

The main concepts are those of a grid of cells, called sheet, with either raw data, called values, or formulas in the cells. Formulas say how to mechanically compute new values from existing values. Values are generally numbers, but can be also pure text, dates, months, etc. Extensions of these concepts include logical spreadsheets. Various tools for programming sheets, visualizing data, remotely connecting sheets, displaying cells dependencies, etc. are commonly provided.

Cells

A "cell" can be thought of as a box for holding data. A single cell is usually referenced by its column and row (A2 would represent the cell below containing the value 10). Usually rows, representing the dependant variables, are referenced in decimal notation starting from 1, while columns representing the independent variables use 26-adic bijective numeration using the letters A-Z as numerals. Its physical size can usually be tailored for its content by dragging its height or width at box intersections (or for entire columns or rows by dragging the column or rows headers).

An array of cells is called a sheet or worksheet. It is analogous to an array of variables in a conventional computer program (although certain unchanging values, once entered, could be considered, by the same analogy, constants). In most implementations, many worksheets may be located within a single spreadsheet. A worksheet is simply a subset of the spreadsheet divided for the sake of clarity. Functionally, the spreadsheet operates as a whole and all cells operate as global variables within the spreadsheet ('read' access only except its own containing cell).

A cell may contain a value or a formula, or it may simply be left empty. By convention, formulas usually begin with = sign.

Sheets

In the earliest spreadsheets, cells were a simple two-dimensional grid. Over time, the model has expanded to include a third dimension, and in some cases a series of named grids, called sheets. The most advanced examples allow inversion and rotation operations which can slice and project the data set in various ways.

Formulas

A formula identifies the calculation needed to place the result in the cell it is contained within. A cell containing a formula therefore has two display components; the formula itself and the resulting value. The formula is normally only shown when the cell is selected by "clicking" the mouse over a particular cell; otherwise it contains the result of the calculation.

 Functions

Spreadsheets usually contain a number of supplied functions, such as arithmetic operations (for example, summations, averages and so forth), trigonometric functions, statistical functions, and so forth. In addition there is often a provision foruser-defined functions. In Microsoft Excel these functions are defined using Visual Basic for Applications in the supplied Visual Basic editor, and such functions are automatically accessible on the worksheet. In addition, programs can be written that pull information from the worksheet, perform some calculations, and report the results back to the worksheet. In the figure, the name sq is user-assigned, and function sq is introduced using the Visual Basic editor supplied with Excel. Name Manager displays the spreadsheet definitions of named variables x & y.

Spreadsheet risk

Spreadsheet risk is the risk associated with deriving a materially incorrect value from Excel or a similar spreadsheet application that will be utilised in making a related (usually numerically based) decision. Examples include the valuation of an asset, the determination of financial accounts, the calculation of medicinal doses or the size of load-bearing beam for structural engineering. Therisk may arise from inputting erroneous or fraudulent data values, from mistakes (or incorrect changes) within the logic of the spreadsheet or the omission of relevant updates (e.g. out of date exchange rates). Some single-instance errors have exceeded US$1 billion. Because spreadsheet risk is principally linked to the actions (or inaction) of individuals it is defined as a sub-category of operational risk.

DATABASES

A database is a structured collection of data. The data are typically organized to model relevant aspects of reality (for example, the availability of rooms in hotels), in a way that supports processes requiring this information (for example, finding a hotel with vacancies).

The term database is correctly applied to the data and their supporting data structures, and not to the database management system (DBMS). The database data collection with DBMS is called adatabase system.

 The term database system implies that the data are managed to some level of quality (measured in terms of accuracy, availability, usability, and resilience) and this in turn often implies the use of a general-purpose database management system (DBMS). A general-purpose DBMS is typically a complex software system that meets many usage requirements to properly maintain its databases which are often large and complex.

This is specially the case with client-server, near-real time transactional systems, in which multiple users have access to data, data is concurrently entered and inquired for in ways that preclude single-thread batch processing. Most of the complexity of those requirements are still present with personal, desktop-based database systems.

 Well known DBMSs include Oracle, FoxPro, IBM DB2, Linter, Microsoft Access, Microsoft SQL Server, MySQL, PostgreSQL and SQLite. A database is not generally portable across different DBMS, but different DBMSs can inter-operate to some degree by using standards like SQL and ODBC together to support a single application built over more than one database. A DBMS also needs to provide effective run-time execution to properly support (e.g., in terms of performance, availability, and security) as many database end-users as needed.

A way to classify databases involves the type of their contents, for example: bibliographic, document-text, statistical, or multimedia objects. Another way is by their application area, for example: accounting, music compositions, movies, banking, manufacturing, or insurance.

The term database may be narrowed to specify particular aspects of organized collection of data and may refer to the logical database, to the physical database as data content in computer data storage or to many other database sub-definitions.

 History

 Database concept

 The database concept has evolved since the 1960s to ease increasing difficulties in designing, building, and maintaining complex information systems (typically with many concurrent end-users, and with a large amount of diverse data). It has evolved together with database management systems which enable the effective handling of databases. Though the terms database and DBMS define different entities, they are inseparable: a database's properties are determined by its supporting DBMS. The Oxford English dictionary cites a 1962 technical report as the first to use the term "data-base." With the progress in technology in the areas of processors, computer memory, computer storage and computer networks, the sizes, capabilities, and performance of databases and their respective DBMSs have grown in orders of magnitudes. For decades it has been unlikely that a complex information system can be built effectively without a proper database supported by a DBMS. The utilization of databases is now spread to such a wide degree that virtually every technology and product relies on databases and DBMSs for its development and commercialization, or even may have such embedded in it. Also, organizations and companies, from small to large, heavily depend on databases for their operations.

No widely accepted exact definition exists for DBMS. However, a system needs to provide considerable functionality to qualify as a DBMS. Accordingly its supported data collection needs to meet respective usability requirements (broadly defined by the requirements below) to qualify as a database. Thus, a database and its supporting DBMS are defined here by a set of general requirements listed below. Virtually all existing mature DBMS products meet these requirements to a great extent, while less mature either meet them or converge to meet them.

 Evolution of database and DBMS technology

The introduction of the term database coincided with the availability of direct-access storage (disks and drums) from the mid-1960s onwards. The term represented a contrast with the tape-based systems of the past, allowing shared interactive use rather than daily batch processing.

In the earliest database systems, efficiency was perhaps the primary concern, but it was already recognized that there were other important objectives. One of the key aims was to make the data independent of the logic of application programs, so that the same data could be made available to different applications.

 In the period since the 1970s database technology has kept pace with the increasing resources becoming available from the computing platform: notably the rapid increase in affordable capacity and speed of disk storage, and of main memory. This has enabled ever larger databases and higher throughput to be achieved.

The first generation of general-purpose database systems were navigational, applications typically accessed data by following pointers from one record to another. The two main data models at this time were the hierarchical model, epitomized by IBM's IMS system, and the Codasyl model (Network model), implemented in a number of products such as IDMS.

The relational model, first proposed in 1970 by Edgar F. Codd, departed from this tradition by insisting that applications should search for data by content, rather than by following links. This was considered necessary to allow the content of the database to evolve without constant rewriting of links and pointers. The relational model is made up of ledger-style tables, each used for a different type of entity. Data may be freely inserted, deleted and edited in these tables, with the DBMS (DataBase Management System) doing whatever maintenance needed to present a table view to the application/user. The relational part comes from entities referencing other entities in what is known as one-to-many relationship, like a traditional hierarchical model, and many-to-many relationship, like a navigational (network) model. Thus, a relational model can express both hierarchical and navigational models, as well as its native tabular model, allowing for pure or combined modeling in terms of these three models, as the application requires.

The earlier expressions of the relational model did not make relationships between different entities explicit in the way practitioners were used to back then, but as primary keys and foreign keys. These keys, though, can be also seen as pointers in their own right, stored in tabular form. This use of keys rather than pointers conceptually obscured relations between entities, at least the way it was presented back then. Thus, the wisdom at the time was that the relational model emphasizes search rather than navigation, and that it was a good conceptual basis for a query language, but less well suited as a navigational language. As a result, another data model, the entity-relationship model which emerged shortly later (1976), gained popularity for database design, as it emphasized a more familiar description than the earlier relational model. Later on, entity-relationship constructs were retrofitted as a data modeling construct for the relational model, and the difference between the two have become irrelevant.

Earlier relational system implementations lacked the sophisticated automated optimizations of conceptual elements and operations versus their physical storage and processing counterparts, present in modern DBMSs (DataBase Management Systems), so their simplistic and literal implementations placed heavy demands on the limited processing resources at the time. It was not until the mid 1980s that computing hardware became powerful enough to allow relational systems (DBMSs plus applications) to be widely deployed. By the early 1990s, however, relational systems were dominant for all large-scale data processing applications, and they remain dominant today (2012) except in niche areas. The dominant database language is the standard SQL for the Relational model, which has influenced database languages for other data models.

The rigidity of the relational model, in which all data are held in related tables with a fixed structure of rows and columns, has increasingly been seen as a limitation when handling information that is richer or more varied in structure than the traditional "ledger-hook' data of corporate information systems. These limitations come to play when modeling document databases, engineering databases, multimedia databases, or databases used in the molecular sciences.

 Most of that rigidity, though, is due to the need to represent new data types other than text and text-alikes within a relational model. Examples of unsupported data types are :

• graphics (and operations such as pattern-matching and OCR)

• Multidimensional constructs such as 2D (geographical), 3D (geometrical), and multidimensional hypercube models (data analysis).

 • XML (an hierarchical data modeling technology evolved from EDS and HTML), used for data interchange among dissimilar systems.

 More fundamental conceptual limitations came with Object Oriented methodologies, with their emphasis on encapsulating data and processes (methods), as well as expressing constructs such as events or triggers. Traditional data modeling constructs emphasize the total separation of data from processes, though modern DBMS do allow for some limited modeling in terms of validation rules and stored procedures.

Various attempts have been made to address this problem, many of them banners such as post-relational or NoSQL. Two developments of note are the object database and the XIVIL database. The vendors of relational databases have fought off competition from these newer models by extending the capabilities of their own products to support a wider variety of data types.

 Database type examples

The following are examples of various database types. Some of them are not main-stream types, but most of them have received special attention (e.g., in research) due to end-user requirements. Some exist as specialized DBMS products, and some have their functionality types incorporated in existing general-purpose DBMSs. Though may differ in nature and functionality, these various types typically have to comply with the usability requirements below to comply as databases.

• Active database

An active database is a database that includes an event-driven architecture which can respond to conditions both inside and outside the database. Possible uses include security monitoring, alerting, statistics gathering and authorization. Most modern relational databases include active database features in the form of database trigger.

• Cloud database

A Cloud database is a database that relies on cloud technology. Both the database and most of its DBMS reside remotely, "in the cloud," while its applications are both developed by programmers and later maintained and utilized by (application's) end-users through a web browser and Open APIs. More and more such database products are emerging, both of new vendors and by virtually all established database vendors.

• Data warehouse

Data warehouses archive data from operational databases and often from external sources such as market research firms. Often operational data undergo transformation on their way into the warehouse, getting summarized, anonymized, reclassified, etc. The warehouse becomes the central source of data for use by managers and other end-users who may not have access to operational data. For example, sales data might be aggregated to weekly totals and converted from internal product codes to use UPCs so that they can be compared with ACNielsendata. Some basic and essential components of data warehousing include retrieving, analyzing, and mining data, transforming,loading and managing data so as to make them available for further use.

Operations in a data warehouse are typically concerned with bulk data manipulation, and as such, it is unusual and inefficient to target individual rows for update, insert or delete. Bulk native loaders for input data and bulk SQL passes for aggregation are the norm.

• Distributed database

The definition of a distributed database is broad, and may be utilized in different meanings. In general it typically refers to a modular DBMS architecture that allows distinct DBMS instances to cooperate as a single DBMS over processes, computers, and sites, while managing a single database distributed itself over multiple computers, and different sites. Examples are databases of local work-groups and departments at regional offices, branch offices, manufacturing plants and other work sites. These databases can include both segments shared by multiple sites, and segments specific to one site and used only locally in that site.

• Document-oriented database

A document-oriented database is a computer program designed for storing, retrieving, and managing document-oriented, or semi structured data, information. Document-oriented databases are one of the main categories of so-called NoSQL databases and the popularity of the term "document-oriented database" (or "document store") has grown with the use of the term NoSQL itself. Utilized to conveniently store, manage, edit and retrieve documents.

• Embedded database

An embedded database system is a DBMS which is tightly integrated with an application software that requires access to stored data in a way that the DBMS is "hidden" from the application's end-user and requires little or no ongoing maintenance. It is actually a broad technology category that includes DBMSs with differing properties and target markets. The term "embedded database" can be confusing because only a small subset of embedded database products is used in real-time embedded systems such as telecommunications switches andconsumer electronics devices.

• End-user database

These databases consist of data developed by individual end-users. Examples of these are collections of documents, spreadsheets, presentations, multimedia, and other files. Several products exist to support such databases. Some of them are much simpler than full fledged DBMSs, with more elementary DBMS functionality (e.g., not supporting multiple concurrent end-users on a same database), with basic programming interfaces, and a relatively small "foot-print" (not much code to run as in "regular" general-purpose databases). However, also available general-purpose DBMSs can often be used for such purpose, if they provide basic user-interfaces for straightforward database applications (limited query and data display; no real programming needed), while still enjoying the database qualities and protections that these DBMSs can provide.

• Federated database and multi-database

A federated database is an integrated database that comprises several distinct databases, each with its own DBMS. It is handled as a single database by a federated database management system (FDBMS), which transparently integrates multiple autonomous DBMSs, possibly ofdifferent types (which makes it a heterogeneous database), and provides them with an integrated conceptual view. The constituent databases are interconnected via computer network, and may be geographically decentralized.

Sometime the term multi-database is used as a synonym to federated database, though it may refer to a less integrated (e.g., without an FDBMS and a managed integrated schema) group of databases that cooperate in a single application. In this case typically middleware for distribution is used which typically includes an atomic commit protocol (ACP), e.g., the two-phase commit protocol, to allow distributed (global) transactions (vs. local transactions confined to a single DBMS) across the participating databases.

• Graph database

 A graph database is a kind of NoSQL database that uses graph structures with nodes, edges, and properties to represent and store information. General graph databases that can store any graph are distinct from specialized graph databases such as triplestores and network databases.

• Hypermedia databases

The World Wide Web can be thought of as a database, albeit one spread across millions of independent computing systems. Web browsers "process" these data one page at a time, whileweb crawlers and other software provide the equivalent of database indexes to support search and other activities.

• Hypertext database

 In a Hypertext database, any word or a piece of text representing an object, e.g., another piece of text, an article, a picture, or a film, can be linked to that object. Hypertext databases are particularly useful for organizing large amounts of disparate information. For example they are useful for organizing online encyclopedias, where users can conveniently jump in the texts, in a controlled way, by using hyperlinks.

 • In-memory database

 An in-memory database (IMDB; also main memory database or MMDB) is a database that primarily resides in main memory, but typically backed-up by non-volatile computer data storage. Main memory databases are faster than disk databases. Accessing data in memory reduces the I/O reading activity when, for example, querying the data. In applications where response time is critical, such as telecommunications network equipment, main memory databases are often used.

• Parallel database

A parallel database, run by a parallel DBMS, seeks to improve performance through parallelization for tasks such as loading data, building indexes and evaluating queries. Parallel databases improve processing and input/output speeds by using multiple central processing units (CPUs) (including multi-core processors) and storage in parallel. In parallel processing, many operations are performed simultaneously, as opposed to serial, sequential processing, where operations are performed with no time overlap.

The major parallel DBMS architectures (which are induced by the underlying hardware architecture are:

ü  Shared memory architecture, where multiple processors share the main memory space, as well as other data storage.

ü  Shared disk architecture, where each processing unit (typically consisting of multiple processors) has its own main memory, but all units share the other storage.

ü  Shared nothing architecture, where each processing unit has its own main memory and other storage.

• Spatial database

 A spatial database can store the data with multidimensional features. The queries on such data include location based queries, like "where is the closest hotel in my area".

• Temporal database

 A temporal database is a database with built-in time aspects, for example a temporal data model and a temporal version of Structured Query Language (SQL). More specifically the temporal aspects usually include valid-time and transaction-time.

• Unstructured-data database

An unstructured-data database is intended to store in a manageable and protected way diverse objects that do not fit naturally and conveniently in common databases. It may include email messages, documents, journals, multimedia objects etc. The name may be misleading since some objects can be highly structured. However, the entire possible object collection does not fit into a predefined structured framework. Most established DBMSs now support unstructured data in various ways, and new dedicated DBMSs are emerging.

 Major database functional areas

 The functional areas are domains and subjects that have evolved in order to provide proper answers and solutions to the functional requirements above.

Data models

A data model is an abstract structure that provides the means to effectively describe specific data structures needed to model an application. As such a data model needs sufficient expressive power to capture the needed aspects of applications. These applications are often typical to commercial companies and other organizations (like manufacturing, human-resources, stock, banking, etc.). For effective utilization and handling it is desired that a data model is relatively simple and intuitive. This may be in conflict with high expressive power needed to deal with certain complex applications. Thus any popular general-purpose data model usually well balances between being intuitive and relatively simple, and very complex with high expressive power. The application's semantics is usually not explicitly expressed in the model, but rather implicit (and detailed by documentation external to the model) and hinted to by data item types' names (e.g., "part-number") and their connections (as expressed by generic data structure types provided by each specific model).

Database languages

 Database languages are dedicated programming languages, tailored and utilized to

 • define a database (i.e., its specific data types and the relationships among them),

 • manipulate its content (e.g., insert new data occurrences, and update or delete existing ones), and

• query it (Le., request information: compute and retrieve any information based on its data).

 Database languages are data-model-specific, i.e., each language assumes and is based on a certain structure of the data (which typically differs among different data models). They typically have commands to instruct execution of the desired operations in the database. Each such command is equivalent to a complex expression (program) in a regular programming language, and thus programming in dedicated (database) languages simplifies the task of handling databases considerably. An expressions in a database language is automatically transformed (by a compiler or interpreter, as regular programming languages) to a proper computer program that runs while accessing the database and providing the needed results. The following are notable examples:

• 4.2.1 SQL for the relational model

• 4.2.2 OQL for the object model

• 4.2.3 XQuery for the XML model

 Implementation: database management systems

A database management system (DBMS) is a system that allows to build and maintain databases, as well as to utilize their data and retrieve information from it. A DBMS implements solutions (see Major database functional areas above) to the database usability requirements above. It defines the database type that it supports, as well as its functionality and operational capabilities. A DBMS provides the internal processes for external applications built on them. The end-users of some such specific application are usually exposed only to that application and do not directly interact with the DBMS. Thus end-users enjoy the effects of the underlying DBMS, but its internals are completely invisible to end-users. Database designers and database administrators interact with the DBMS through dedicated interfaces to build and maintain the applications' databases, and thus need some more knowledge and understanding about how DBMSs operate and the DBMSs' external interfaces and tuning parameters.

A DBMS consists of software that operates databases, providing storage, access, security, backup and other facilities to meet needed requirements. DBMSs can be categorized according to thedatabase model(s) that they support, such as relational or XML, the type(s) of computer they support, such as a server cluster or a mobile phone, the query language(s) that access the database, such as SQL or XQuery, performance trade-offs, such as maximum scale or maximum speed or others. Some DBMSs cover more than one entry in these categories, e.g., supporting multiple query languages. Database software typically support the Open Database Connectivity (ODBC) standard which allows the database to integrate (to some extent) with other databases.

The development of a mature general-purpose DBMS typically takes several years and many man-years. Developers of DBMS typically update their product to follow and take advantage of progress in computer and storage technologies. Several DBMS products like Oracle and IBM D82 have been in on-going development since the 1970s-1980s. Since DBMSs comprise a significanteconomical market, computer and storage vendors often take into account DBMS requirements in their own development plans.

Database storage

 Database storage is the container of the physical materialization of a database. It comprises the Internal (physical) level in the database architecture. It also contains all the information needed (e.g., metadata, "data about the data", and internal data structures) to reconstruct the conceptual level and external level from the Internal level when needed. It is not part of the DBMS but rather manipulated by the DBMS (by its Storage engine; see above) to manage the database that resides in it. Though typically accessed by a DBMS through the underlying operating system (and often utilizing the operating systems' file systems as intermediates for storage layout), storage properties and configuration setting are extremely important for the efficient operation of the DBMS, and thus are closely maintained by database administrators. A DBMS, while in operation, always has its database residing in several types of storage (e.g., memory and external storage). The database data and the additional needed information, possibly in very large amounts, are coded into bits. Data typically reside in the storage in structures that look completely different from the way the data look in the conceptual and external levels, but in ways that attempt to optimize (the best possible) these levels' reconstruction when needed by users and programs, as well as for computing additional types of needed information from the data (e.g., when querying the database).

 In principle the database storage can be viewed as a linear address space, where every bit of data has its unique address in this address space. Practically only a very small percentage of addresses is kept as initial reference points (which also requires storage), and most of the database data are accessed by indirection using displacement calculations (distance in bits from the reference points) and data structures which define access paths (using pointers) to all needed data in an effective manner, optimized for the needed data access operations.

PA 'T 3

"Creative Software"

Graphic Design

Graphic design is a creative process—most often involving a client and a designer and usually completed in conjunction with producers of form (i.e., printers, signmakers, etc.)—undertaken in order to convey a specific message (or messages) to a targeted audience. The term "graphic design" can also refer to a number of artistic and professional disciplines that focus on visual communication and presentation. The field as a whole is also often referred to as Visual Communication or Communication Design. Various methods are used to create and combine words, symbols, and images to create a visual representation of ideas and messages. A graphic designer may use a combination of typography, visual arts and page layout techniques to produce the final result. Graphic design often refers to both the process (designing) by which the communication is created and the products (designs) which are generated.

Common uses of graphic design include identity (logos and branding), publications (magazines, newspapers, and books), advertisements and product packaging. For example, a product package might include a logo or other artwork, organized text and pure design elements such as shapes and color which unify the piece. Composition is one of the most important features of graphic design, especially when using pre-existing materials or diverse elements.

History

While Graphic Design as a discipline has a relatively recent history, with the term "graphic design" first coined by William Addison Dwiggins in 1922, graphic design-like activities span the history of humankind: from the caves of Lascaux, to Rome's Trajan's Column to the illuminated manuscripts of the Middle Ages, to the dazzling neons of Ginza. In both this lengthy history and in the relatively recent explosion of visual communication in the 20th and 21st centuries, there is sometimes a blurring distinction and over-lapping of advertising art, graphic design and fine art. After all, they share many of the same elements, theories, principles, practices and languages, and sometimes the same benefactor or client. In advertising art the ultimate objective is the sale of goods and services. In graphic design, "the essence is to give order to information, form to ideas, expression and feeling to artifacts that document human experience."

The advent of printing

During the Tang Dynasty (618-907) between the 7th and 9th century AD, wood blocks were cut to print on textiles and later to reproduce Buddhist texts. A Buddhist scripture printed in 868 is the earliest known printed book. Beginning in the 11th century, longer scrolls and books were produced using movable type printing making books widely available during the Song dynasty (960-1279). Sometime around 1450, Johann Gutenberg's printing press made books widely available in Europe. The book design of Aldus Manutius developed the book structure which would become the foundation of western publication design. This era of graphic design is called Humanist or Old Style.

Emergence of the design industry

In late 19th century Europe, especially in the United Kingdom, the movement began to separate graphic design from fine art.

In 1849, Henry Cole became one of the major forces in design education in Great Britain, informing the government of the importance of design in hislournal of Design and Manufactures. He organized the Great Exhibition as a celebration of modern industrial technology and Victorian design.

From 1891 to 1896, William Morris' Kelmscott Press published books that are some of the most significant of the graphic design products of the Arts and Crafts movement, and made a very lucrative business of creating books of great stylistic refinement and selling them to the wealthy for a premium. Morris proved that a market existed for works of graphic design in their own right and helped pioneer the separation of design from production and from fine art. The work of the Kelmscott Press is characterized by its obsession with historical styles. This historicism was, however, important as it amounted to the first significant reaction to the stale state of nineteenth-century graphic design. Morris' work, along with the rest of the Private Press movement, directly influenced Art Nouveau and is indirectly responsible for developments in early twentieth century graphic design in general.

Twentieth century design

The name "Graphic Design" first appeared in print in the 1922 essay "New Kind of Printing Calls for New Design" by William Addison Dwiggins, an American book designer in the early 20th century.

Raffe's Graphic Design, published in 1927, is considered to be the first book to use "Graphic Design" in its title.

The signage in the London Underground is a classic design example' of the modern era and used a typeface designed by Edward Johnston in 1916.

In the 1920s, Soviet constructivism applied 'intellectual production' in different spheres of production. The movement saw individualistic art as useless in revolutionary Russia and thus moved towards creating objects for utilitarian purposes. They designed buildings, theater sets, posters, fabrics, clothing, furniture, logos, menus, etc.

Jan Tschichold codified the principles of modern typography in his 1928 book, New Typography. He later repudiated the philosophy he espoused in this book as being fascistic, but it remained very influential, Tschichold, Bauhaus typographers such as Herbert Bayer and Laszlo Moholy-Nagy, and El Lissitzky have greatly influenced graphic design as we know it today. They pioneered production techniques and stylistic devices used throughout the twentieth century. The following years saw graphic design in the modern style gain widespread acceptance and application. A booming post-World War II American economy established a greater need for graphic design, mainly advertising and packaging. The emigration of the German Bauhaus school of design to Chicago in 1937 brought a "mass-produced" minimalism to America; sparking a wild fire of "modern" architecture and design. Notable names in mid- century modern design include Adrian Frutiger, designer of the typefaces Univers and Frutiger; Paul Rand, who, from the late 1930s until his death in 1996, took the principles of the Bauhaus and applied them to popular advertising and logo design, helping to create a uniquely American approach to European minimalism while becoming one of the principal pioneers of the subset of graphic design known as corporate identity; and Josef Multer-Brockmann, who designed posters in a severe yet accessible manner typical of the 1950s and 1970s era.

The growth of the professional graphic design industry has grown in parallel with the rise

of consumerism. This has raised some concerns and criticisms, notably from within the graphic design community with the First Things First manifesto. First launched by Ken Garland in 1964, it was re­published as the First Things First 2000 manifesto in 1999 in the magazine Emigre 51 stating "We propose a reversal of priorities in favor of more useful, lasting and democratic forms of communication - a mindshift away from product marketing and toward the exploration and production of a new kind of meaning. The scope of debate is shrinking; it must expand. Consumerism is running uncontested; it must be challenged by other perspectives expressed, in part, through the visual languages and resources of design." Both editions attracted signatures from respected design practitioners and thinkers, for example; Rudy VanderLans, Erik Spiekermann, Ellen Lupton andRick Poynor. The 2000 manifesto was also notably published in Adbusters, known for its strong critiques of visual culture.

Applications

From road signs to technical schematics, from interoffice memorandums to reference manuals, graphic design enhances transfer of knowledge and visual messages. Readability and legibility is enhanced by improving the visual presentation and layout of text.

Design can also aid in selling a product or idea through effective visual communication. It is applied to products and elements of company identity likelogos, colors, packaging, and text. Together these are defined as branding (see also advertising). Branding has increasingly become important in the range of services offered by many graphic designers, alongside corporate identity. Whilst the terms are often used interchangeably, branding is more strictly related to the identifying mark or trade name for a product or service, whereas corporate identity can have a broader meaning relating to the structure and ethos of a company, as well as to the company's external image. Graphic designers will often form part of a team working on corporate identity and branding projects. Other members of that team can include marketing professionals, communications consultants and commercial writers.

Textbooks are designed to present subjects such as geography, science, and math. These publications have layouts which illustrate theories anddiagrams. A common example of graphics in use to educate is diagrams of human anatomy. Graphic design is also applied to layout and formatting of educational material to make the information more accessible and more readily understandable.

Graphic design is applied in the entertainment industry in decoration, scenery, and visual story telling. Other examples of design for entertainment purposes include novels, comic books, DVD covers, opening credits and closing credits in filmmaking, and programs and props on stage. This could also include artwork used for t-shirts and other items screenprinted for sale.

From scientific journals to news reporting, the presentation of opinion and facts is often improved with graphics and thoughtful compositions of visual information - known as information design. Newspapers, magazines, blogs, television and film documentaries may use graphic design to inform and entertain. With the advent of the web, information designers with experience in interactive tools such as Adobe Flash are increasingly being used to illustrate the background to news stories.

Skills

A graphic design project may involve the stylization and presentation of existing text and either preexisting imagery or images developed by the graphic designer. For example, a newspaper story begins with the journalists and photojournalists and then becomes the graphic designer's job to organize the page into a reasonable layout and determine if any other graphic elements should be required. In a magazine article or advertisement, often the graphic designer or art director will commission photographers or illustrators to create original pieces just to be incorporated into the design layout. Or the designer may utilize stock imagery or photography. Contemporary design practice has been extended to the modern computer, for example in the use of WYSIWYG user interfaces, often referred to as interactive design, or multimedia design.

Visual arts

Before any graphic elements may be applied to a design, the graphic elements must be originated by means of visual art skills. These graphics are often (but not always) developed by a graphic designer. Visual arts include works which are primarily visual in nature using anything from traditional media, to photography or computer generated art. Graphic design principles may be applied to each graphic art element individually as well as to the final composition.

Typography

Typography is the art, craft and techniques of type design, modifying type glyphs, and arranging type. Type glyphs (characters) are created and modified using a variety of illustration techniques. The arrangement of type is the selection of typefaces, point size, tracking (the space between all characters used), kerning (the space between two specific characters), and leading (line spacing).

Typography is performed by typesetters, compositors, typographers, graphic artists, art directors, and clerical workers. Until the Digital Age, typography was a specialized occupation. Digitization opened up typography to new generations of visual designers and lay users.

Page layout

The page layout aspect of graphic design deals with the arrangement of elements (content) on a page, such as image placement, and text layout and style. Beginning from early illuminated pages in hand- copied books of the Middle Ages and proceeding down to intricate modern magazine and catalogue layouts, structured page design has long been a consideration in printed material. With print media, elements usually consist of type (text), images (pictures), and occasionally place-holder graphics for elements that are not printed with ink such as die/laser cutting, foil stamping orblind embossing.

Interface design

Since the advent of the World Wide Web and computer software development, many graphic designers have become involved in interface design. This has included web design and software design, when end user interactivity is a design consideration of the layout or interface. Combining visual communication skills with the interactive communication skills of user interaction and online branding, graphic designers often work with software developers and web developers to create both the look and feel of a web site or software application and enhance the interactive experience of the user or web site visitor. An important aspect of interface design is icon design.

User experience design

Considers how a user interacts with and responds to an interface, service or product and adjusts it accordingly.

Printmaking

Printmaking is the process of making artworks by printing on paper and other materials or surfaces. Except in the case of monotyping, the process is capable of producing multiples of the same piece, which is called a print. Each piece is not a copy but an original since it is not a reproduction of another work of art and is technically known as an impression. Painting or drawing, on the other hand, create a unique original piece of artwork. Prints are created from a single original surface, known technically as a matrix. Common types of matrices include: plates of metal, usually copper or zinc for engraving or etching; stone, used for lithography; blocks of wood for woodcuts, linoleum for linocuts and fabric plates for screen-printing. But there are many other kinds, discussed below. Works printed from a single plate create an edition, in modern times usually each signed and numbered to form a limited edition. Prints may also be published in book form, as artist's books. A single print could be the product of one or multiple techniques.

Tools

The mind may be the most important graphic design tool. Aside from technology, graphic design requires judgment and creativity. Critical, observational, quantitative and analytic thinking are required for design layouts and rendering. If the executor is merely following a solution (e.g. sketch, script or instructions) provided by another designer (such as an art director), then the executor is not usually considered the designer.

The method of presentation (e.g. arrangement, style, medium) may be equally important to the design. The layout is produced using external traditionalor digital image editing tools. The appropriate development and presentation tools can substantially change how an audience perceives a project.

In the mid 1980s, the arrival of desktop publishing and graphic art software applications introduced a generation of designers to computer image manipulation and creation that had previously been manually executed. Computer graphic design enabled designers to instantly see the effects of layout or typographic changes, and to simulate the effects of traditional media without requiring a lot of space. However, traditional tools such as pencils ormarkers are useful even when computers are used for finalization; a designer or art director may hand sketch numerous concepts as part of the creative process. Some of these sketches may even be shown to a client for early stage approval, before the designer develops the idea further using a computer and graphic design software tools.

Computers are considered an indispensable tool in the graphic design industry. Computers and software applications are generally seen by creative professionals as more effective productiontools than traditional methods. However, some designers continue to use manual and traditional tools for production, such as Milton Glaser.

New ideas can come by way of experimenting with tools and methods. Some designers explore ideas using pencil and paper. Others use many different mark-making tools and resources from computers to sculpture as a means of inspiring creativity. One of the key features of graphic design is that it makes a tool out of appropriate image selection in order to possibly convey meaning.

Computers and the creative process

there is some debate wheter computers enhance the creative process of graphic design. Rapid production from the computer allows many designers to explore multiple ideas quickly with more detail than what could be achieved by traditional hand-rendering or paste-up on paper, moving the designer through the creative process more quickly. However, being faced with limitless choices does not help isolate the best design solution and can lead to endless iterations with no clear design outcome.

A graphic designer may use sketches to explore multiple or complex ideas quickly without the distractions and complications of software. Hand-rendered comps are often used to get approval for an idea execution before a designer invests time to produce finished visuals on a computer or in paste-up. The same thumbnail sketches or rough drafts on paper may be used to rapidly refine and produce the idea on the computer in a hybrid process. This hybrid process is especially useful in logo design where a software learning curve may detract from a creative thought process. The traditional-design/computer-production hybrid process may be used for freeing one's creativity in page layout or image development as well. In the early days of computer publishing, many "traditional" graphic designers relied on computer-savvy production artists to produce their ideas from sketches, without needing to learn the computer skills themselves. However, this practice has been increasingly less common since the advent of desktop publishing over 30 years ago. The use of computers and graphics software is now taught in most graphic design courses.

 Nearly all of the popular and "industry standard" software programs used for graphic design since the early 1990s are products of Adobe Systems Incorporated. They are Adobe Photoshop (a raster-based program for photo editing), Adobe Illustrator (a vector-based program for drawing), Adobe InDesign (a page layout program), and Adobe Dreamweaver (for Web page design). Another major page layout tool is QuarkXpress (a product of Quark, Inc., a separate company from Adobe). Both QuarkXpress and Adobe InDesign are often used in the final stage of the electronic design process. Raster images may have been edited in Adobe Photoshop, logos and illustrations in Adobe Illustrator, and the final product assembled in one of the major page layout programs. Most graphic designers entering the field since about 1990 are expected to be proficient in at least one or two of these programs.

Occupations

Graphic design career paths cover all ends of the creative spectrum and often overlap. The main job responsibility of a Graphic Designer is the arrangement of visual elements in some type of media. The main job titles within the industry can vary and are often country specific. They can include graphic designer, art director, creative director, and the entry level production artist. Depending on the industry served, the responsibilities may have different titles such as "DTP Associate" or "Graphic Artist", but despite changes in title, graphic design principles remain consistent. The responsibilities may come from, or lead to, specialized skills such as illustration, photography or interactive design. Today's graduating graphic design students are normally exposed to all of these areas of graphic design and urged to become familiar with all of them as well in order to be competitive.

Graphic designers can work in a variety of environments. Whilst many will work within companies devoted specifically to the industry, such as design consultancies or branding agencies, others may work within publishing, marketing or other communications companies. Increasingly, especially since the introduction of personal computers to the industry, many graphic designers have found themselves working within non-design oriented organizations, as in-house designers. Graphic designers may also work as free-lance designers, working on their own terms, prices, ideas, etc.

A graphic designer reports to the art director, creative director or senior media creative. As a designer becomes more senior, they may spend less time designing media and more time leading and directing other designers on broader creative activities, such as brand development and corporate identity development. They are often expected to interact more directly with clients, for example taking and interpreting briefs.

Web design

Web design encompasses many different skills and disciplines in the production and maintenance of websites. The different areas of web design include web graphic design; interface design; authoring, including standardised code and proprietary software; user experience design; and search engine optimization. Often many individuals will work in teams covering different aspects of the design process, although some designers will cover them all. The term web design is normally used to describe the design process relating to the front-end (client side) design of a website including writing mark up, but this is a grey area as this is also covered by web development. Web designers are expected to have an awareness of usability and if their role involves creating mark up then they are also expected to be up to date with web accessibility guidelines.

History (1988-2001)

Although web design has a fairly recent history, it can be linked to other areas such as graphic design. However web design is also seen as a technological standpoint. It has become a large part of people's everyday lives. It is hard to imagine the Internet without animated graphics, different styles of typography, background and music.

The start of the web and web design

In 1989, whilst working at CERN Tim Berners-Lee proposed to create a global hypertext project, which later became known as the World Wide Web. Throughout 1991 to 1993 the World Wide Web was born. Text only pages could be viewed using a simple line-mode browser. In 1993 Marc Andreessen and Eric Bina, created the Mosaic browser. At the time there were multiple browsers however the majority of them were Unix-based and were naturally text heavy. There had been no integrated approach to graphical design elements such as images or sounds. The Mosaic browser broke this mould. The W3C was created in October 1994, to "lead the World Wide Web to its full potential by developing common protocols that promote its evolution and ensure its interoperability." This discouraged any one company from monopolizing a propriety browser and programming language, which could have altered the effect of the World Wide Web as a whole. The W3C continues to set standards, which can today be seen with JavaScript. In 1994 Andreessen formed Communications corp. That later became known as Netscape Communications the Netscape 0.9 browser. Netscape created its own HTML tags without regards to the traditional standards process. For example Netscape 1.1 included tags for changing background colours and formatting text with tables on web pages. Throughout 1996 to 1999 the browser wars began. The browser wars saw Microsoft and Netscape battle it out for the ultimate browser dominance. During this time there were many new technologies in the field, notably Cascading Style Sheets, JavaScript, and Dynamic HTML. On a whole the browser competition did lead to many positive creations and helped web design evolve at a rapid pace.

Evolution of web design

In 1996, Microsoft released its first competitive browser, which was complete with its own features and tags. It was also the first browser to support style sheets, which at the time was seen as an obscure authoring technique. The HTML markup for tables was originally intended for displaying tabular data. However designers quickly realized the potential of using HTML tables for creating the complex, multi-column layouts that were otherwise not possible. At this time, as design and good aesthetics seemed to take precedence over good mark-up structure, and little attention was paid to semantics and web accessibility. HTML sites were limited in their design options, even more so with earlier versions of HTML. To create complex designs, many web designers had to use complicated table structures or even use blank spacer .GIF images to stop empty table cells from collapsing. CSS was introduced in December 1996 by the W3C to support presentation and layout; this allowed HTML code to be semantic rather than both semantic and presentational, and improved web accessibility, see tableless web design. In 1996 Flash (originally known as FutureSplash) was developed. At the time it was of a very simple layout basic tools and a timeline but it enabled web designers to go beyond the point of HTML at the time. It has now progressed to be very powerful, enabling it to develop entire sites.

End of the first browser wars

During 1998 Netscape released Netscape Communicator code under an open source licence, enabling thousands of developers to participate in improving the software. However they decided to stop and start from the beginning, which guided the development of the open source browser and soon expanded to a complete application platform. The Web Standards Project was formed, and promoted browser compliance with HTML and CSS standards by creating Acidl, Acid2, and Acid3 tests. 2000 was a big year for Microsoft. Internet Explorer had been released for Mac, this was significant as it was the first browser that fully supported HTML 4.01 and CSS 1, raising the bar in terms of standards compliance. It was also the first browser to fully support the PNG image format. During this time Netscape was sold to AOL and this was seen as Netscape's official loss to Microsoft in the browser wars.

History (2001-2012)

Since the start of the 215` century the web has become more and more integrated into peoples lives, as this has happened the technology of the web has also moved on. There have also been signifigent changes in the way people use and access the web, this has changed how sites are designed.

The Modern Browsers

Since the end of the browsers wars there have been new browsers coming onto the scence, many of these are open source meaning that they tend to have faster development and are more supportive of new standards. The new options are considered by many to be better that Microsoft's Internet Explorer.

New Standards

The W3C has released new standards of HTML (HTM15) and CSS (CSS3), as well as new JavaScript API's each as a new but individual standard, however while the term HTML5 is only used to refer to the new version of HTML and some of the JavaScript API's, it has become common to use it to refer to the entire suite of new standards (HTML5, CSS3 and JavaScript)

Tools and technologies

Web designers use a variety of different tools depending on what part of the production process they are involved in. These tools are updated over time by newer standards and software but the principies behind them remain the same. Web graphic designers use vector and raster graphics packages for creating web formatted imagery or design prototypes. Technologies used for creating websites include standardised mark up which oauld be hand coded or generated by WYSIWYG editing software. There is also proprietary software based on plug-ins that bypasses the dient's browsers version, these are often WYSIWYG but with the option of using the softwareis scripting language. Search engine optimisation tools may be used to check search engine ranking and suggest improvements.

Other tools web designers might use include mark up validators and other testing tools for usability and accessibility to ensure their web sites meet web accessibility guidelines.

Skills and techniques

 Typography

Usually a successful website has only a few typefaces which are of a similar style, instead of using a range of typefaces. Preferably a website should use sans serif or serif typefaces, not a combination of the two. Typography in websites should also be careful the amount of typefaces used, good design will incorporate a few similar typefaces rather than a range of type faces. Most browsers recognize a specific nurnber of safe fonts, which designers mainly use in order to avoid complications.

Font downloading was later included in the CSS3 fonts module, and has since been implemented in Safari 3.1, Opera 10 and Mozilla Firefox 3.5. This has subsequently increased interest in Web typography, as well as the usage of font downloading.

Most layouts on a site incorporate white spaces to break the text up into paragraphs and also avoid centre aligned text.

 Page layout

Web pages should be well laid out to improve navigation for the user. Also for navigation purposes, the sites page layout should also remain consistent on different pages. When constructing sites, it’s important to consider page width as this is vital for aligning objects and in layout design. The most popular websites generally have a width close to 1024 pixels. Most pages are also centre aligned, to make objects look more aesthetically pleasing on larger screens.

Fluid tayouts developed around 2000 as a replacement for HTML-table-based layouts, as a rejection of grid-based design both as a page layout design principle, and as a coding technique, but were very slow to be adopted. The axiomatic assumption is that readers will have screen devices, or windows thereon, of different sizes and that there is nothing the page designer can do to change this. Accordingly, a design should be broken down into units (sidebars, content blocks, advert areas, navigation areas) that are sent to the browser and which will be fitted into the display window by the browser, as best it can. As the browser does know the details of the reader's screen (window size, font size relative to window etc.) the browser does a better job of this than a presumptive designer. Although such a display may often change the relative position of major content units, sidebars may be displaced below body text rather than to the side of it, this is usually a better and particularly a more usable display than a compromise attempt to display a hard-coded grid that simply doesn't fit the device window. In particular, the relative position of content blocks may change, but each block is less affected. Usability is also better, particularly by the avoidance of horizontal scrolling.

Responsive Web Design is a new approach, based on CSS3, and a deeper level of per-device specification within the page's stylesheet, through an enhanced use of the CSS @media pseudo-selector.

Quality of code

 When creating a site it is good practice to conform to standards. This is usually done via a description specifying what the element is doing. Not conforming to standards may not make a website unusable or error prone, standards can relate to the correct layout of pages for readability as well making sure coded elements are closed appropriately. This includes errors in code, better layout for code as well as making sure your IDs and classes are identified properly. Poorly-coded pages are sometimes colloquially called tag soup. Validating via W3C can only be done when a correct DOCTYPE declaration is made, which is used to highlight errors in code. The system identifies the errors and areas that do not conform to web design standards. This inforrnation can then be corrected by the user.

 Visual design

Good visual design on a website identifies and works for its target market. This can be an age group or particular strand of culture thus the designer shoutd understand the trends of its audience. Designers should also understand the type of website they are designing, meaning a business website should not be designed the same as a social media site for example. Designers should also understand the owner or business the site is representing, to make sure they are portrayed favourably. The aesthetics or overall design of a site should not clash with the content, making it easier for the user to navigate and can find the desired information or products etc.

User experience design

 For a user to understand a website they must be able to understand how the website works. This affects their experience. User experience is related to layout, clear instructions and labelling on a website. The user must understand how they can interact on a site. ln relation to continued use, a user must perceive the usefulness of that website if they are to continue using it. With users who are skilled and well versed with website use, this influence relates directly to how they perceive websites, which encourages further use. Therefore users with less experience are tess likely to see the advantages or usefulness of websites. This in turn should focus, on design for a more universal use and ease of access to accommodate as many users as possible regardless of user skill.

Occupations

 There are two primary jobs involved in creating a website: the web designer and web developer, who often work closely together on a website. The web designers are responsible for the visuat aspect, which includes the layout, colouring and typography of a web page. A web designer will also have a working knowledge of using a variety of languages such as HTML, CSS, JavaScript, PHP and Flash to create a site, although the extent of their knowiedge will differ from one web ciesigner to another. Particularly in smaller organizations one person will need the necessary skills for designing and programming the full web page, whilst larger organizations may have a web designer responsible for the visual aspect alone.

Further jobs, which under particular circumstances may become involved during the creation of a website include:

•        Graphic designers, to create visuals for the site such as logos, layouts and buttons

·         Internet marketing specialists, to help maintain web presence through strategic solutions on targeting viewers to the site, by using marketing and promotional techniques on the internet.

·         SEO writers, to research and recommend the correct words to be incorporated into a particular website and make the website more accessible and found on numerous search engines.

·           Internet copywriter, to create the written content of the page to appeal to the targeted viewers of the site.

·          User experience (UX) designer, incorporates aspects of user focused design considerations which include information architecture, user centred design, user testing, interaction design, and occasionally visual design.

Multimedia

Multimedia is media and content that uses a combination of different content forms. This contrasts with media that use only rudimentary computer displays such as text-only or traditional forms of printed or hand-produced material. Multimedia includes a combination of text, audio, still images, animation, video, or interactivity content forms.

Multimedia is usually recorded and played, displayed, or accessed by information content processing devices, such as computerized and electronic devices, but can also be part of a live performance. Multimedia devices are electronic media devices used to store and experience multimedia content. Multimedia is distinguished from mixed media in fine art; by including audio, for example, it has a broader scope. The term "rich media" is synonymous for interactive multimedia. Hypermedia can be considered one particular multimectia application.

 Categorization of multimedia

Multimedia may be broadly divided into linear and non-linear categories. Linear active content progresses often without any navigational control for the viewer such as a cinema presentation. Non-linear uses interactivity to control progress as with a video game or self-paced computer based training. Hypermedia is an example of non-linear content.

 Multimedia presentations can be live or recorded. A recorded presentation may allow interactivity via a navigation system. A live multimedia presentation may allow interactivity via an interaction with the presenter or performer.

 Major characteristics of multimedia

 Multimedia presentations may be viewed by person on stage, projected, transmitted, or played locally with a media player. A broadcast may be a live or recorded multimedia presentation. Broadcasts and recordings can be either analog or digital electronic media technology. Digital online multimedia may be downloaded or streamed. Streaming multimedia may be live or on-demand.

Multimedia games and simulations may be used in a physical environment with special effects, with multiple users in an online network, or locally with an offline computer, game system, orsimuiator.

The various formats of technological or digital multimedia may be intended to enhance the users' experience, for example to make it easier and faster to convey information. Or in entertainment or art, to transcend everyday experience.

 Enhanced levels of interactivity are made possible by combining multiple forms of media content. Online multimedia is increasingly becoming object-oriented and data-driven, enabling applications with collaborative end-user innovation and personalization on multiple forms of content over time. Examples of these range from multiple forms of content on Web sites like photo galleries with both images (pictures) and title (text) user-updated, to simulations whose co-efficients, events, illustrations, animations or videos are modifiable, allowing the multimedia "experience" to be altered without reprogramming. In addition to seeing and hearing, Haptic technology enables virtual objects to be felt. Emerging technology involving illusions of taste and smell may also enhance the multimedia experience.

Terminology

History of the term

The term multimedia was coined by singer and artist Bob Goldstein (later 'Bobb Goldsteinn') to promote the July 1966 opening of his "LightWorks at L'Oursin" show at Southampton, Long Island. Goldstein was perhaps aware of a British artist named Dick Higgins, who had two years previously discussed a new approach to art-making he called "intermedia."

On August 10, 1966, Richard Albarino of Variety borrowed the terminology, reporting: "Brainchild of songscribe-comic Bob (`Washington Square') Goldstein, the `Lightworks' is the latest multi-media music-cum-visuals to debut as discotheque fare." Two years later, in 1968, the term "multimedia" was re-appropriated to describe the work of a political consultant, David Sawyer, the husband of Iris Sawyer—one of Goldstein's producers at L'Oursin.

In the intervening forty years, the word has taken on different meanings. In the late 1970s, the term referred to presentations consisting of multi-projector slide shows timed to an audio track. However, by the 1990s 'multimedia' took on its current meaning.

In the 1993 first edition of McGraw-Hill's Multimedia: Making It Work, Tay Vaughan declared "Multimedia is any combination of text, graphic art, sound, animation, and video that is delivered by computer. When you allow the user—the viewer of the project — to control what and when these elements are delivered, it is interactive multimedia. When you provide a structure of linked elements through which the user can navigate, interactive multimedia becomes hypermedia."

 The German language society, Gesellschaft fiir deutsche Sprache, decided to recognize the word's significance and ubiquitousness in the 1990s by awarding it the title of 'Word of the Year' in 1995. The institute summed up its rationale by stating "[Multimedia] has become a central word in the wonderful new media world"

In common usage, multimedia refers to an electronically delivered combination of media including video, still images, audio, text in such a way that can be accessed interactively. Much of the content on the web today falls within this definition as understood by millions. Some computers which were marketed in the 1990s were called "multimedia" computers because they incorporated a CD-ROM drive, which allowed for the delivery of several hundred megabytes of video, picture, and audio data. That era saw also a boost in the production of educational multimedia application CD-ROMs.

Word usage and context

Since media is the plural of medium, the term "multimedia" is used to describe multiple occurrences of only one form of media such as a collection of audio CDs. This is why it's important that the word "multimedia" is used exclusively to describe multiple forms of media and content.

 The term "multimedia" is also ambiguous. Static content (such as a paper book) may be considered multimedia if it contains both pictures and text or may be considered interactive if the user interacts by turning pages at will. Books may also be considered non-linear if the pages are accessed non-sequentially. The term "video", if not used exclusively to describe motion photography, is ambiguous in multimedia terminology. Video is often used to describe the file format, delivery format, or presentation format instead of "footage" which is used to distinguish motion photography from "animation" of rendered motion imagery. Multiple forms of information content are often not considered modern forms of presentation such as audio or video. Likewise, single forms of information content with single methods of information processing (e.g. non-interactive audio) are often called multimedia, perhaps to distinguish static media from active media. In the Fine arts, for example, Leda Luss Luyken's ModulArt brings two key elements of musical composition and film into the world of painting: variation of a theme and movement of and within a picture, makingModu/Art an interactive multimedia form of art. Performing arts may also be considered multimedia considering that performers and props are multiple forms of both content and media.

Usage / Application

Multimedia finds its application in various areas including, but not limited to, advertisements, art, education, entertainment, engineering, medicine,mathematics, business, scienti fic research and spatial temporal applications. Several examples are as follows:

Creative industries

Creative industries use multimedia for a variety of purposes ranging from fine arts, to entertainment, to commercial art, to journalism, to media and software services provided for any of the industries listed below. An individual multimedia designer may cover the spectrum throughout their career. Request for their skills range from technical, to analytical, to creative.

 Commercial uses

Much of the electronic old and new media used by commercial artists is multimedia. Exciting presentations are used to grab and keep attention inadvertising. Business to business, and interoffice communications are often developed by creative services firms for advanced multimedia presentations beyond simple slide shows to sell ideas or liven-up training. Commercial multimedia developers may be hired to design for governmental services andnonprofit services applications as well.

Entertainment and fine arts

In addition, multimedia is heavily used in the entertainment industry, especially to develop special effects in movies and animations. Multimedia games are a popular pastime and are software programs available either as CD-ROMs or online. Some video games also use multimedia features. Multimedia applications that allow users to actively participate instead of just sitting by as passive recipients of information are called Interactive Multimedia. In theArts there are multimedia artists, whose minds are able to blend techniques using different media that in some way incorporates interaction with the viewer. One of the most relevant could be Peter Greenaway who is melding Cinema with Opera and all sorts of digital media. Another approach entails the creation of multimedia that can be displayed in a traditional fine arts arena, such as an art gallery. Although multimedia display material may be volatile, the survivability of the content is as strong as any traditional media. Digital recording material may be just as durable and infinitely reproducible with perfect copies every time.

Education

In Education, multimedia is used to produce computer-based training courses (popularly called CBTs) and reference books like encyclopedia and almanacs. A CBT lets the user go through a series of presentations, text about a particular topic, and associated illustrations in various information formats. Edutainment is the combination of education with entertainment, especially multimedia entertainment.

Learning theory in the past decade has expanded dramatically because of the introduction of multimedia. Several lines of research have evolved (e.g.Cognitive load, Multimedia learning, and the list goes on). The possibilities for learning and instruction are nearly endless.

The idea of media convergence is also becoming a major factor in education, particularly higher education. Defined as separate technologies such as voice (and telephony features), data (and productivity applications) and video that now share resources and interact with each other, synergistically creating new efficiencies, media convergence is rapidly changing the curriculum in universities all over the world. Likewise, it is changing the availability, or lack thereof, of jobs requiring this savvy technological skill.

The English education in middle school in China is well invested and assisted with various equipments. In contrast, the original objective has not been achieved at the desired effect. The government, schools, families, and students spend a lot of time working on improving scores, but hardly gain practical skills. English education today has gone into the vicious circle. Educators need to consider how to perfect the education system to improve students' practical ability of English. Therefore an efficient way should be used to make the class vivid. Multimedia teaching will bring students into a class where they can interact with the teacher and the subject. Multimedia teaching is more intuitive than old ways; teachers can simulate situations in real life. In many circumstances teachers don't have to be there, students will learn by themselves in the class. More importantly, teachers will have more approaches to stimulating students' passion of learning

Journalism

Newspaper companies all over are also trying to embrace the new phenomenon by implementing its practices in their work. While some have been slow to come around, other major newspapers like The New York Times, USA Today and The Washington Post are setting the precedent for the positioning of the newspaper industry in a globalized world.

 News reporting is not limited to traditional media outlets. Freelance journalists can make use of different new media to produce multimedia pieces for their news stories. It engages global audiences and tells stories with technology, which develops new communication techniques for both media producers and consumers. Common Language Project is an example of this type of multimedia journalism production.

Multimedia reporters who are mobile (usually driving around a community with cameras, audio and video recorders, and wifi-equipped laptop computers) are often referred to as Mojos, from mobilejournalist.

 Engineering

Software engineers may use multimedia in Computer Simulations for anything from entertainment to training such as military or industrial training. Multimedia for software interfaces are often done as a collaboration between creative professionals and software engineers.

Industry

 In the Industrial sector, multimedia is used as a way to help present information to shareholders, superiors and coworkers. Multimedia is also helpful for providing employee training, advertising and selling products all over the world via virtually unlimited web-based technology

Mathematical and scientific research

 In mathematical and scientific research, multimedia is mainly used for modeling and simulation. For example, a scientist can look at a molecular model of a particular substance and manipulate it to arrive at a new substance. Representative research can be found in journals such as the Journal of Multimedia.

Medicine

In Medicine, doctors can get trained by looking at a virtual surgery or they can simulate how the human body is affected by diseases spread by viruses and bacteria and then develop techniques to prevent it.

 Document imaging

Document imaging is a technique that takes hard copy of an image/document and converts it into a digital format (for example, scanners).

Disabilities
Ability Media allows those with disabilities to gain qualifications in the multimedia field so they can pursue careers that give them access to a wide array of powerful communication forms.

Miscellaneous
In Europe, the reference organisation for Multimedia industry is the European Multimedia Associations Convention (EMMAC).

ART 4

"Programming"

                                 

Programming

  Computer programming (often shortened to programming, scripting, or coding) is the process of designing, writing, testing, debugging, and maintaining the source code of computer programs. This source code is written in one or more programming languages (such as Java, C++, C#,Python, etc.). The purpose of programming is to create a set of instructions that computers use to perform specific operations or to exhibit desired behaviors. The process of writing source code often requires expertise in many different subjects, including knowledge of the application domain, specialized algorithms and formal logic. Within software engineering, programming (the implementation) is regarded as one phase in a software development process.

 There is an ongoing debate on the extent to which the writing of programs is an art form, a craft, or an engineering discipline. In general, good programming is considered to be the measured application of all three, with the goal of producing an efficient and evolvable software solution (the criteria for "efficient" and "evolvable" vary considerably). The discipline differs from many other technical professions in that programmers, in general, do not need to be licensed or pass any standardized (or governmentally regulated) certification tests in order to call themselves "programmers" or even "software engineers." Because the discipline covers many areas, which may or may not include critical applications, it is debatable whether licensing is required for the profession as a whole. in most cases, the discipline is self-governed by the entities which require the programming, and sometimes very strict environments are defined (e.g. United States Air Force use of AdaCore and security clearance). However, representing oneself as a "Professional Software Engineer" without a license from an accredited institution is illegal in many parts of the world.

Another ongoing debate is the extent to which the programming language used in writing computer programs affects the form that the final program takes. This debate is analogous to that surrounding the Sapir—Whorf hypothesis in linguistics and cognitive science, which postulates that a particular spoken language's nature influences the habitual thought of its speakers. Different language patterns yield different patterns of thought. This idea challenges the possibility of representing the world perfectly with language, because it acknowledges that the mechanisms of any language condition the thoughts of its speaker community.

History

 Ancient cultures had no conception of computing beyond simple arithmetic. The only mechanical device that existed for numerical computation at the beginning of human history was the abacus, invented in Sumeria circa 2500 BC. Later, the Antikythera mechanism, invented some time around 100 AD in ancient Greece, was the first mechanical calculator utilizing gears of various sizes and configuration to perform calculations, which tracked themetonic cycle still used in lunar-to-solar calendars, and which is consistent for calculating the dates of the Olympiads. The Kurdish medieval scientistAI-Jazari built programmable Automata in 1206 AD. One system employed in these devices was the use of pegs and cams placed into a wooden drum at specific locations, which would sequentially trigger levers that in turn operated percussion instruments. The output of this device was a small drummer playing various rhythms and drum patterns. The Jacquard Loom, which Joseph Marie Jacquard developed in 1801, uses a series ofpasteboard cards with holes punched in them. The hole pattern represented the pattern that the loom had to follow in weaving cloth. The loom could produce entirely different weaves using different sets of cards. Charles Babbage adopted the use of punched cards around 1830 to control his Analytical Engine. The first computer program was written for the Analytical Engine by mathematician Ada Lovelace to calculate a sequence of Bernoulli Numbers. The synthesis of numerical calculation, predetermined operation and output, along with a way to organize and input instructions in a manner relatively easy for humans to conceive and produce, led to the modern development of computer programming. Development of computer programming accelerated through the Industrial Revolution.

 In the late 1880s, Herman Hollerith invented the recording of data on a medium that could then be read by a machine. Prior uses of machine readable media, above, had been for control, not data. "After some initial trials with paper tape, he settled on punched cards..." To process these punched cards, first known as "Hollerith cards" he invented the tabulator, and the keypunch machines. These three inventions were the foundation of the modern information processing industry. In 1896 he founded the Tabulating Machine Company (which later became the core of IBM). The addition of a control panel (plugboard) to his 1906 Type I Tabulator allowed it to do different jobs without having to be physically rebuilt. By the late 1940s, there were a variety of control panel programmable machines, called unit record equipment, to perform data-processing tasks.

The invention of the von Neumann architecture allowed computer programs to be stored in computer memory. Early programs had to be painstakingly crafted using the instructions (elementary operations) of the particular machine, often in binary notation. Every model of computer would likely use different instructions (machine language) to do the same task. Later, assembly languages were developed that let the programmer specify each instruction in a text format, entering abbreviations for each operation code instead of a number and specifying addresses in symbolic form (e.g., ADD X, TOTAL). Entering a program in assembly language is usually more convenient, faster, and less prone to human error than using machine language, but because an assembly language is little more than a different notation for a machine language, any two machines with different instruction sets also have different assembly languages.

 In 1954, FORTRAN was invented; it was the first high level programming language to have a functional implementation, as opposed to just a design on paper. (A high-level language is, in very general terms, any programming language that allows the programmer to write programs in terms that are more abstract than assembly language instructions, i.e. at a level of abstraction "higher" than that of an assembly language.) it allowed programmers to specify calculations by entering a formula directly (e.g.Y = X*2 + 5*X + 9). The program text, or source, is converted into machine instructions using a special program called a compiler, which translates the FORTRAN program into machine language. In fact, the name FORTRAN stands for "Formula Translation". Many other languages were developed, including some for commercial programming, such as COBOL. Programs were mostly still entered using punched cards or paper tape. (See computer programming in the punch card era). By the late 1960s, data storage devices and computer terminals became inexpensive enough that programs could be created by typing directly into the computers. Text editors were developed that allowed changes and corrections to be made much more easily than with punched cards. (Usually, an error in punching a card meant that the card had to be discarded and a new one punched to replace it.)

As time has progressed, computers have made giant leaps in the area of processing power. This has brought about newer programming languages that are more abstracted from the underlying hardware. Popular programming languages of the modern era include C++, C#, Objective-C, Visual Basic, SQL, HTML with PHP, ActionScript, Perl, Java, JavaScript, Ruby, Python, Haskell and dozens more. Although these high-level languages usually incur greater overhead, the increase in speed of modern computers has made the use of these languages much more practical than in the past. These increasingly abstracted languages typically are easier to learn and allow the programmer to develop applications much more efficiently and with less source code. However, high-level languages are still impractical for a few programs, such as those where low-level hardware control is necessary or where maximum processing speed is vital. Computer programming has become a popular career in the developed world, particularly in theUnited States, Europe, Scandinavia, and Japan. Due to the high labor cost of programmers in these countries, some forms of programming have been increasingly subject to offshore outsourcing (importing software and services from other countries, usually at a lower wage), making programming career decisions in developed countries more complicated, while increasing economic opportunities for programmers in less developed areas, particularly China and India.

 Programming languages

Different programming languages support different styles of programming (called programming paradigms). The choice of language used is subject to many considerations, such as company policy, suitability to task, availability of third-party packages, or individual preference. Ideally, the programming language best suited for the task at hand will be selected. Trade-offs from this ideal involve finding enough programmers who know the language to build a team, the availability of compilers for that language, and the efficiency with which programs written in a given language execute. Languages form an approximate spectrum from "low-level" to "high-level"; "low-level" languages are typically more machine-oriented and faster to execute, whereas "high-level" languages are more abstract and easier to use but execute less quickly. It is usually easier to code in "high-level" languages than in "low-level" ones.

Allen Downey, in his book How To Think Like A Computer Scientist, writes: The details look different in different languages, but a few basic instructions appear in just about every language:

• input: Gather data from the keyboard, a file, or some other device.

• output: Display data on the screen or send data to a file or other device.

• arithmetic: Perform basic arithmetical operations like addition and multiplication.

• conditional execution: Check for certain conditions and execute the appropriate sequence of statements.

• repetition: Perform some action repeatedly, usually with some variation.

Many computer languages provide a mechanism to call functions provided by libraries such as in a .so. Provided the functions in a library follow the appropriate run time conventions (e.g., method of passing arguments), then these functions may be written in any other language.

 Programmers

 Computer programmers are those who write computer software. Their jobs usually involve:

• Coding

• Compilation

• Debugging

• Documentation

 • Integration

• Maintenance

• Requirements analysis

• Software architecture

• Software testing

• Specification

PA T

"Computer Tomorrow"

Electronic Communication Network

An electronic communication network (ECN) is a financial term for a type of computer system that facilitates trading of financial products outside of stock exchanges. The primary products that are traded on ECNs are stocks and currencies. The first ECN, Instinet, was created in 1969. ECNs increase competition among trading firms by lowering transaction costs, giving clients full access to their order books, and offering order matching outside of traditional exchange hours. ECNs are sometimes also referred to as Alternative Trading Systems or Alternative Trading Networks.

Function

To trade with an ECN, one must be a subscriber or have an account with a broker that provides direct access trading. ECN subscribers can enter orders into the ECN via a custom computer terminal or network protocols. The ECN will then match contra-side orders (i.e. a sell-order is "contra-side" to a buy-order with the same price and share count) for execution. The ECN will post unmatched orders on the system for other subscribers to view. Generally, the buyer and seller are anonymous, with the trade execution reports listing the ECN as the party.

Some ECN brokers may offer additional features to subscribers such as negotiation, reserve size, and pegging, and may have access to the entire ECN book (as opposed to the "top of the book") that real-time market data regarding depth of trading interest.

ECNs are generally facilitated by electronic negotiation, a type of communication between agents that allows cooperative and competitive sharing of information to determine a proper price.

Negotiation types

The most common paradigm is the electronic auction type. As of 2005, most e-business negotiation systems can only support price negotiations. Traditional negotiations typically include discussion of other attributes of a deal, such as delivery terms or payment conditions. This one-dimensional approach is one of the reasons why electronic markets struggle for acceptance. Multiattributive and combinatorial auction mechanisms are emerging to allow further types of negotiation.

 Support for complex multi-attribute negotiations is a critical success factor for the next generation of electronic markets and, more generally, for all types of electronic exchanges. This is what the second type of Electronic negotiation, namely Negotiation Support, addresses. While auctions are essentially mechanisms, bargaining is often the only choice in complex cases or those cases where no choice of partners is given. Bargaining is a hard, error-prone, ambiguous task often performed under time pressure. Information technology has some potential to facilitate negotiation processes which is analyzed in research projects/prototypes such as INSPIRE, Negoisst or WebNS.

 The third type of negotiation is automated argumentation, where agents exchange not only values, but also arguments for their offers/counter-offers. This requires agents to be able to reason about the mental states of other market participants.

Technologies

One research area that has paid particular attention to modeling automated negotiations is that of autonomous agents. If negotiations occur frequently, possibly on a minute per minute basis in order

to schedule network capacity, or negotiation topics can be clearly defined it may be desirable to automate this coordination effort.

Automated negotiation is a key form of interaction in complex systems composed of autonomous agents. Negotiation is a process of making offers and counteroffers, with the aim of finding an acceptable agreement. During negotiation, each offer is based on its own utility and expectation of what other. This means that a multi criteria decision making is need to be taken for each offer.

In the stock market

For stock trading, ECNs exist as a class of SEC-permitted Alternative Trading Systems (ATS). As an ATS, ECNs exclude broker-dealers' internal crossing networks — i.e., systems that match orders in private using prices from a public exchange.

Fee structure

ECN's fee structure can be grouped in two basic structures: a classic structure and a credit (or rebate) structure. Both fee structures offer advantages of their own. The classic structure tends to attract liquidity removers while the credit structure appeals to liquidity providers. However since both removers and providers of liquidity are necessary to create a market, ECNs must choose their fee structures carefully.

In a credit structure ECNs make a profit from paying liquidity providers a credit while charging a debit to liquidity removers. Credits range from $0.002 to $0.00295 per share for liquidity providers, and debits from $0.0025 to $0.003 per share for liquidity removers. The fee can be determined by monthly volume provided and removed, or by a fixed structure, depending on the ECN. This structure is common on the NASDAQ market. NASDAQ Price List. Traders commonly quote the fees in millicents or mils (e.g. $0.00295 is 29.5 mils).

 In a classic structure, the ECN will charge a small fee to all market participants using their network, both liquidity providers and removers. They also can attract volume to their networks by giving lower prices to large liquidity providers. Fees for ECNs that operate under a classic structure range from $0 to $0.0015, or even higher depending on each ECN. This fee structure is more common in the NYSE, however recently some ECNs have moved their NYSE operations into a credit structure.

Currency trading

The first ECN for Internet currency trading was New-York based Matchbook FX formed in 1999. Back then, all the prices were created & supplied by Matchbook FX's traders/users, including banks, within its ECN network. This was quite unique at the time, as it empowered buy-side FX market participants, historically always "price takers", to finally be price makers as well. Today, FX ECNs like Currenex, Bloomberg Tradebook (an affiliate of Bloomberg L.P.), Hotspot FX, 360T, FXall & BAXTER Financial Services Ltd with Currency Dealing provide access to an electronic trading network, supplied with streaming quotes from the top tier banks in the world. Their matching engines perform limit checks and match orders, usually in less than 100 milliseconds per order. The matching is quote driven and these are the prices that match against all orders. Spreads are discretionary but in general multibank competition creates 1-2 pip spreads on USD Majors and Euro Crosses. The order book is not a routing system that sends orders to individual market makers. It is a live exchange type book working against the best bid/offer of all quotes. By trading through an ECN, a currency trader generally benefits from greater price transparency, faster processing, increased liquidity and more availability in the marketplace. Banks also reduce their costs as there is less manual effort involved in using an ECN for trading.

History

 One of the key developments in the history of ECNs was the NASDAQ over-the-counter quotation system. NASDAQ was created following a 1969 American Stock Exchange study which estimated that errors in the processing of hand-written securities orders cost brokerage firms approximately $100 million per year. The NASDAQ system automated such order processing and provided brokers with the latest competitive price quotes via a computer terminal. In March 1994, a study by two economists, William Christie and Paul Schultz, noted that NASDAQ hid-ask spreads were larger than was statistically likely, indicating "We are unable to envision any scenario in which 40 to 60 dealers who are competing for order flow would simultaneously and consistently avoid using odd-eighth quotes without an implicit agreement to post quotes only on the even price fractions. However, our data do not provide direct evidence of tacit collusion among NASDAQ market makers." These results led to an antitrust lawsuit being filed against NASDAQ. As part of NASDAQ's settlement of the antitrust charges, NASDAQ adopted new order handling rules that integrated ECNs into the NASDAQ system. Shortly after this settlement, the SEC adopted Regulation ATS, which permitted ECNs the option of registering as stock exchanges or else being regulated under a separate set of standards for ECNs.

 At that time major ECNs that became active were Instinet and Island (part of instinet was spun off, merged with Island into met, and acquired by NASDAQ), Archipelago Exchange (which was acquired by the NYSE) and Brut (now acquired by NASDAQ).

ECNs enjoyed a resurgence after the adoption of SEC Regulation NMS, which required "trade through" protection of orders in the market, regardless of where those orders are placed.

Remember when the Internet was known as the "information super highway"? Currently, the Internet is often called Web 2.0. And who knows what we'll call it a few years from now. Though relatively young in the grand scheme of things, the Internet has evolved rapidly. Today's Internet is a far cry from yesteryear, and though its future has yet to materialize, one thing is certain: Tomorrow's Internet will be yet another incarnation.

Internet Issues

The Internet's Past

 The Internet is a child of the 1960s, with its roots dating back to 1969 when the first network of computers, ARPANET, communicated with one another. It took a full decade before the Internet Protocol was developed. In 1984, the domain name system was created, bringing with it the familiar suffixes of .com and .org.

Still primarily academic, the Internet wasn't widely used until the 1990s when two significant developments arrived. In 1991, the World Wide Web was ushered in. Hyperlinks made navigation much easier than in the past. And in 1993, the first Web browser, Mosaic, arrived, making for a graphical user experience. By the mid-1990s, an estimated 45 million users were using the Internet. By 2000, that number exploded to over 400 million. The Internet was officially here to stay.

In its early incarnation, users connected to the Internet primarily through dial-up networking which consisted of a modem and a phone line. Users would connect, search for information, check email messages, and then disconnect once these tasks were complete thus freeing the phone line for traditional phone calls.

The Internet Today

 Today the Internet isn't a side activity; it's a main attraction. High-speed, broadband connections have largely replaced dial-up networking. Now, many computer users are connected to the Internet around the clock. In addition, mobile phones and other devices such as PDAs and gaming consoles now connect to the Internet.

While yesterday's websites were static, today's sites are dynamic. It is a social medium where users are engaged. We shop online, we bank online, we play games online, we read the news online, we listen to music on line, we make phone calls online, we watch TV and movies online, we connect with other users online, we create our own media online, we do business online, and the list goes on. The Internet has affected nearly everything that we do.

 In the past, we purchased music and software on CDs. Today, many users buy music downloads while others subscribe to unlimited streaming music subscriptions. Software is now available as a service "in the cloud." Rather than buying a disc, installing the software, and owning it outright, software can be accessed online via a monthly subscription.

 Along with the advances made comes a darker side: computer viruses, spyware, and privacy concerns. Hackers and malware developers are running rampant, fueling a cat-and-mouse game between the black hatters and computer security experts. In addition privacy concerns have been raised. Not only does malware threaten privacy, some users willingly and unwittingly give up personal information online over social networks and some people are concerned about the potential for government monitoring.

 The Internet's Future

 If you could gaze into a crystal ball and see the Internet in the future, what would it look like? No one knows for sure, but we can speculate. With the popularity of mobile devices such as the iPad, cell phones, and eBook readers, it's likely that the Internet will continue to spread into other areas of our lives. Touch screens and voice recognition technologies may render the keyboard and mouse obsolete. It's also likely that more content will be delivered via the Internet than over traditional media such as radio, television, print, and CDs. Cloud computing may also become more prevalent.

The Internet has been fascinating the world on a grand scale for nearly two decades. It is sure to continue its evolution, surprising us with its wonders for decades to come.

 Interested in the Internet, VolP, cloud computing, and virtualization? CBT Planet offers a huge selection of computer training courses covering all aspects of technology. Whether you want to specialize in networking or master an emerging technology, CBT Planet offers live and self-paced instructor-led training designed with your learning needs in mind. Numerous formats are offered including CBT training, online training videos, distance learning, onsite training, and IT boot camps.

New Technology

Windows 8

Windows 8 is the current release of the Windows operating system, produced by Microsoft for use on personal computers, including home and business desktops, laptops, tablets, and home theater PCs. Development of Windows 8 started before the release of its predecessor in 2009. Its existence was first  announced at CES 2011, and followed by the release of three pre-release versions from September 2011 to May 2012. The operating system was released to manufacturing on August 1, 2012, and was released for general availability on October 26, 2012.

Windows 8 introduces significant changes to the operating system's platform, primarily focused towards improving its user experience on mobile devices such as tablets to rival other mobile operating systems like Android and i0S, taking advantage of new or emerging technologies like USB 3.0, UEFI firmware, near field communications, cloud computing and the low-power ARM architecture, new security features such as malware filtering, built-in antivirus capabilities, a new installation process optimized for digital distribution, and support for secure boot (a UEFI feature which allows operating systems to be digitally signed to prevent malware from altering the boot process), the ability to synchronize certain apps and settings between multiple devices, along with other changes and performance improvements. Windows 8 also introduces a new shell and user interface based on Microsoft's "Metro" design language, featuring a new Start screen with a grid of dynamically updating tiles to represent applications, a new app platform with an emphasis on touchscreen input, and the newWindows Store to obtain and/or purchase applications to run on the operating system.

Windows 8 was released to mixed reception—although reception towards its performance improvements, security enhancements, and its improved support for touchscreen devices was positive, the new user interface of the operating system has been widely criticized for being confusing and having a steep learning curve (especially when used with a keyboard and mouse instead of a touchscreen). Despite these shortcomings, 40 million Windows 8 licenses were sold during its first month of availability, mostly to original equipment manufacturers(OEMs).

Software compatibility

The three desktop editions of Windows 8 are sold in two sub-editions: 32-bit and 64-bit. The 32-bit sub- edition runs on CPUs compatible with x86 architecture 3rd generation (known as IA-32) or newer, and can only run 32-bit programs. The 64-bit sub-edition runs on CPUs compatible with x86 8th

generation (known as x86-64, or x64) or newer, and can run 32-bit and 64-bit programs. 32-bit programs and operating system are restricted to supporting only 4 gigabytes of memory while 64-bit systems can theoretically support 2048 gigabytes of memory. 64-bit operating system require a different set of device drivers than those of 32-bit operating systems.

The 32-bit edition of Windows 8 is capable of running 16-bit applications, although 16-bit support must be enabled first. 16-bit applications are developed for CPUs compatible with x86 2nd generation, first conceived in 1978. Microsoft started moving away from this architecture since Windows 95.

Windows RT, the only edition of Windows 8 for systems with ARM processors, only supports applications included with the system (such as a special version of Office 2013), supplied through Windows Update, or Windows Store apps, to ensure that the system only runs applications that are optimized for the architecture. Windows RT does not support running IA-32 or x64 applications. Windows Store apps can either be cross-compatible between Windows 8 and Windows RT, or compiled to support a specific architecture.

New and changed features

New features and functionality in Windows 8 include a faster startup through UEFI integration and the new "Hybrid Boot" mode (which hibernates the Windows kernel on shutdown to speed up the subsequent boot), a new lock screen with a clock and notifications, and the ability for enterprise users to create live USB versions of Windows (known as Windows To Go). Windows 8 also adds native support for USB 3.0 devices, which allow for faster data transfers and improved power management with compatible devices, along with support for near field communicationto facilitate sharing and communication between devices.

Windows Explorer, which has been renamed File Explorer, now includes a ribbon in place of the command bar. File operation dialog boxes have been updated to provide more detailed statistics, the ability to pause file transfers, and improvements in the ability to manage conflicts when copying files. A new "File History" function allows incremental revisions of files to be backed up to and restored from a secondary storage device, while Storage Spaces allows users to combine different sized hard disks into virtual drives and specify mirroring, parity, or no redundancy on a folder-by-folder basis.

Task Manager has also been redesigned, including a new processes tab with the option to display fewer or more details of running applications and background processes, a heat map using different colors indicating the level of resource usage, network and disk counters, grouping by process type (e.g. applications, background processes and Windows processes), friendly names for processes and a new option which allows users to search the web to find information about obscure processes. Additionally, the Blue Screen of Death has been updated with a simpler and modern design with less technical information displayed.

Android (operating system)

Android is a Linux-based operating system designed primarily for touchscreen mobile devices such as smartphones and tablet computers. Initially developed by Android, Inc., whom Google financially backed and later purchased in 2005, Android was unveiled in 2007 along with the founding of the Open Handset Alliance: a consortium of hardware, software, and telecommunication companies devoted to advancing open standards for mobile devices. The first Android-powered phone was sold in October

2008.

Android is open source and Google releases the code under the Apache License. This open source code and permissive licensing allows the software to be freely modified and distributed by device manufacturers, wireless carriers and enthusiast developers. Additionally, Android has a large community of developers writing applications ("apps") that extend the functionality of devices, written primarily in a customized version of the Javaprogramming language. In October 2012, there were approximately 700,000 apps available for Android, and the estimated number of applications downloaded from Google Play, Android's primary app store, was 25 billion.

These factors have allowed Android to become the world's most widely used smartphone platform and the software of choice for technology companies who require a low-cost, customizable, lightweight operating system for high tech devices without developing one from scratch. As a result, despite being primarily designed for phones and tablets, it has seen additional applications on televisions, games consoles and other electronics. Android's open nature has further encouraged a large community of developers and enthusiasts to use the open source code as a foundation for community-driven projects, which add new features for advanced users or bring Android to devices which were officially released running other operating systems.

Android had a worldwide smartphone market share of 75% during the third quarter of 2012, with 500 million devices activated in total and 1.3 million activations per day. The operating system's success has made it a target for patent litigation as part of the so-called "smartphone wars" between technology companies.

Description

Interface

Android's user interface is based on direct manipulation, using touch inputs that loosely correspond to real-world actions, like swiping, tapping, pinching and reverse pinching to manipulate on-screen objects. The response to user input is designed to be immediate and provides a fluid touch interface, often using the vibration capabilities of the device to provide haptic feedback to the user. Internal hardware such as accelerometers, gyroscopes and proximity sensors are used by some applications to respond to additional user actions, for example adjusting the screen from portrait to landscape depending on how the device is oriented, or allowing the user to steer a vehicle in a racing game by rotating the device, simulating control of a steering wheel.

Android devices boot to the homescreen, the primary navigation and information point on the device, which is similar to the desktop found on PCs. Android homescreens are typically made up of app icons and widgets; app icons launch the associated app, whereas widgets display live, auto-updating content such as the weather forecast, the user's email inbox, or a news ticker directly on the homescreen. A homescreen may be made up of several pages that the user can swipe back and forth between, though Android's homescreen interface is heavily customisable, allowing the user to adjust the look and feel of the device to their tastes. Third party apps available on Google Play and other app stores can extensively re-theme the homescreen, and even mimic the look of other operating systems, such as Windows Phone. Most manufacturers, and some wireless carriers, customise the look and feel of their Android devices to differentiate themselves from the competition.

Present along the top of the screen is a status bar, showing information about the device and its connectivity. This status bar can be "pulled" down to reveal a notification screen where apps display important information or updates, such as a newly received email or SMS text, in a way that doesn't immediately interrupt or inconvenience the user. In early versions of Android these notifications could be tapped to open the relevant app, but recent updates have provided enhanced functionality, such as the ability to call a number back directly from the missed call notification without having to open the dialer app first. Notifications are persistent until read or dismissed by the user.

Applications

Android has a growing selection of third party applications, which can be acquired by users either through an app store such as Google Play or the Amazon Appstore, or by downloading and installing the application's APK file from a third-party site. The Play Store application allows users to browse, download and update apps published by Google and third-party developers, and is pre-installed on devices that comply with Google's compatibility requirements. The app filters the list of available applications to those that are compatible with the user's device, and developers may restrict their applications to particular carriers or countries for business reasons. Purchases of unwanted applications can be refunded within 15 minutes of the time of download, and some carriers offer direct carrier billing for Google Play application purchases, where the cost of the application is added to the user's monthly

bill. As of September 2012, there were more than 675,000 apps available for Android, and the estimated number of applications downloaded from the Play Store was 25 billion.

Applications are developed in the Java language using the Android software development kit (SDK). The SDK includes a comprehensive set of development tools, including a debugger, software libraries, a handset emulator based on QEMU, documentation, sample code, and tutorials. The officially supported integrated development environment (IDE) is Eclipse using the Android Development Tools (ADT) plugin. Other development tools are available, including a Native Development Kit for applications or extensions in C or C++, Google App Inventor, a visual environment for novice programmers, and various cross platform mobile web applications frameworks.

In order to work around limitations on reaching Google services due to Internet censorship in the People's Republic of China, Android devices sold in the PRC are generally customized to use state approved services instead.