(Excerpted from The Computer Desktop Encyclopedia by Alan Freedman)

• 3D Studio

A 3-D modeling and animation program for DOS from AutoDesk, Inc., Sausalito, CA. It was the first program to bring professional animation and 3-D rendering from high-end workstations to the PC. Its 2D Shaper module lets you create 2-D shapes that become the cross sections of the 3-D models. 3D Lofter creates the underlying framework of the 3-D model, and 3D Editor is used to prepare the scene for rendering. In Release 4, the Keyframer animation module includes Inverse Kinematics, which links components so that they move together.
A vector graphics image is a collection of graphic elements, such as lines, squares, rectangles and circles. Although grouped together, each element maintains its own integrity and identity and can always be selected and erased or resized independent of all the others.
• Accelerator

A key combination used to activate a task. See accelerator board and graphics accelerator.
• add-in, add-on

Refers to hardware modules, such as printed circuit boards, that are designed to be plugged into a socket within the computer.
• Algorithm

A set of ordered steps for solving a problem, such as a mathematical formula or the instructions in a program. The terms algorithm and logic are synonymous. Both refer to a sequence of steps to solve a problem. However, an algorithm implies an expression that solves a complex problem rather than the overall input-process-output logic of typical business programs.
• alpha channel

High-order eight bits in a 32-bit graphics pixel used as a separate layer to mask an area for editing or creating special effects (textures, montages, etc.).
• Analog

A representation of an object that resembles the original. Analog devices monitor conditions, such as movement, temperature and sound, and convert them into analogous electronic or mechanical patterns. For example, an analog watch represents the planet's rotation with the rotating hands on the watch face. Telephones turn voice vibrations into electrical vibrations of the same shape. Analog implies continuous operation in contrast with digital, which is broken up into numbers.
Advantages and Disadvantages Of Analog Techniques Traditionally, audio and video recording has been analog. Sound, which is continuously varying air vibrations, is converted into analogous electrical vibrations. Video cameras scan their viewing area a line at a time and convert the infinitely varying intensities of light into analogous electrical signals.
The ability to capture the subtle nature of the real world is the single advantage of analog techniques. However, once captured, modern electronic equipment, no matter how advanced, cannot copy analog signals perfectly. Third and fourth generations of audio and video recordings show marked deterioration.
By converting analog signals into digital, the original audio or video data can be preserved indefinitely and copied over and over without deterioration. Once continuously varying analog signals are measured and converted into digital form, they can be stored and transmitted without loss of integrity due to the accuracy of digital methods.
The key to conversion is the amount of digital data that is created from the analog signal. The shorter the time interval between samples and the more data recorded from that sample, the more the digital encoding reflects the original signal.
• Anti-aliasing.

Smoothing the jagged appearance of diagonal lines in a bitmapped image.  The pixels that surround the edges of the line are changed to varying shades of gray or color in order to blend the sharp edge into the background.  This technique is also called dithering, but when it is applied to diagonal and curved lines, it is called anti-aliasing.
• ASCII file.

Data or text file that contains characters coded in ASCII. Text files, word processing documents, batch files and source language programs are usually ASCII files. Only the first 128 characters (0-127) within the 256 combinations in a byte conform to the ASCII standard. The rest are used differently depending on the computer.
• ASCII.

(American Standard Code for Information Interchange) Pronounced "ask-ee." A binary code for data that is used in communications, most minicomputers and all personal computers.
ASCII is a 7-bit code providing 128 possible character combinations, the first 32 of which are used for printing and transmission control. Since the common storage unit is an 8-bit byte (256 combinations) and ASCII uses only 128, the extra bit is used to hold a parity bit or special symbols. For example, the PC uses the additional values for foreign language and graphics symbols. In the Macintosh, the additional values can be user-defined to enhance a font. In the Macintosh version of this Glossary, the IBM PC symbols are designed into the font used for the definitions. See ASCII chart and hex chart.
• bandwidth

The transmission capacity of a computer channel, communications line or bus. It is expressed in cycles per second (Hertz), the bandwidth being the difference between the lowest and highest frequencies transmitted. The frequency is equal to or greater than the bits per second. Bandwidth is also often stated in bits or bytes per second.
• BASIC

(Beginners All purpose Symbolic Instruction Code) Programming language developed by John Kemeny and Thomas Kurtz in the mid 1960s at Dartmouth College. Originally developed as an interactive, mainframe timesharing language, it has become widely used on all sizes of computers including pocket computers.
BASIC is considered one of the easiest programming languages to learn. Simple programs can be quickly written on the fly. However, BASIC is not a structured language, such as Pascal, dBASE or C, and it's easy to write spaghetti code that's difficult to decipher later.
• batch processing

Processing a group of transactions at one time. Transactions are collected and processed against the master files (master files updated) at the end of the day or some other time period. Contrast with transaction processing.
Batch and Transaction Processing Information systems typically use both batch and transaction processing methods. For example, in an order processing system, transaction processing is the continuous updating of the customer and inventory files as orders are entered.
At the end of the day, batch processing programs generate picking lists for the warehouse. At the end of the week or some other period, batch programs print invoices and management reports.
• Bezier

In computer graphics, a curve that is generated using a mathematical formula which assures continuity with other Bezier curves. It is mathematically simpler, but more difficult to blend than a b-spline curve. Within CAD and drawing programs, Bezier curves are typically reshaped by moving the handles that appear off of the curve.
• BIOS

(Basic Input Output System) Detailed instructions that activate peripheral devices. Although BIOSs have been around for more than 30 years, today, the term generally refers to the BIOS in a PC, which holds certain fundamental parts of the operating system. A PC's BIOS has traditionally been stored in a permanent ROM chip and is often referred to as the ROM BIOS. Increasingly, the PC's BIOS is built into a flash memory chip, which can be updated in place by installing the latest version of the routines just like one updates a software application. The motherboard contains a system BIOS, and expansion cards often have their own BIOSs.
The system BIOS includes routines for the keyboard, screen, disk, parallel and serial port and for internal services such as time and date. It accepts requests from the device drivers in the operating system as well as from application programs.
It also contains an autostart routine that tests the system on startup and prepares the computer for operation. It searches for BIOSes on the plug-in boards and sets up pointers (interrupt vectors) in memory to access BIOS routines. It then loads the operating system and passes control to it.
• bit depth

(1) The number of bits used to hold a pixel. Also called color depth and pixel depth, the bit depth determines the number of colors that can be displayed at one time. Digital video requires at least 15 bits, while 24 bits produces realistic TV-like colors.
Color depth Total number of colors
4-bits 16
8-bits 256
15-bits 32,768
16-bits 65,536
24-bits 16,777,216
32-bits 16,777,216 + alpha channel
(2) Bit depth can refer to any coding system that uses numeric values to represent something. The depth, or number of bits, determines how many discrete items can be represented.
• bit

(BInary digiT) Single digit in a binary number (0 or 1). Within the computer, a bit is physically a memory cell (made up of transistors or one transistor and a capacitor), a magnetic spot on disk or tape or a pulse of high or low voltage traveling through a circuit. Conceptually, a bit is like a light bulb; either on or off.
Groups of bits make up storage units in the computer, called characters, bytes, or words, which are manipulated as a group. The most common is the byte, which is made up of eight bits and is equivalent to one alphanumeric character.
• Bitmap

A binary representation in which a bit or set of bits corresponds to some part of an object such as an image or font. For example, in monochrome systems, one bit represents one pixel on screen. For gray scale or color, several bits in the bitmap represent one pixel or group of pixels. The term may also refer to the memory area that holds the bitmap. A bitmap is usually associated with graphics objects, in which the bits are a direct representation of the picture image. However, bitmaps can be used to represent and keep track of anything, where each bit location is assigned a different value or condition.
The image in the bitmap is continuously transmitted to the video screen, dot for dot, a line at a time, over and over again. Any changes made to the bitmap are instantly reflected on the screen.
• bitmapped graphics

The raster graphics method for generating images. Contrast with vector graphics and character graphics. When you scan an image or paint an object into the computer, the image is created in a reserved area of memory called a bitmap, with some number of bits corresponding to each dot (pixel). The simplest monochrome bitmap uses one bit (on/off) for each dot. Gray scale bitmaps (monochrome shades) hold a number for each dot large enough to hold all the gray levels. Color bitmaps require three times as much storage in order to hold the intensity of red, green and blue.
• Boolean logic

The "mathematics of logic," developed by English mathematician George Boole in the mid 19th century. Its rules govern logical functions (true/false). As add, subtract, multiply and divide are the primary operations of arithmetic, AND, OR and NOT are the primary operations of Boolean logic.
• boot

Causing the computer to start executing instructions. Personal computers contain built-in instructions in a ROM chip that are automatically executed on startup. These instructions search for the operating system, load it and pass control to it. Starting up a large computer may require more button pushing and keyboard input. The term comes from "bootstrap," since bootstraps help you get your boots on, booting the computer helps it get its first instructions. See cold boot and warm boot.
• b-spline.

In computer graphics, a curve that is generated using a mathematical formula which assures continuity with other b-splines.
• buffer

A reserved segment of memory used to hold data while it is being processed. In a program, buffers are created to hold some amount of data from each of the files that will be read or written. A buffer may also be a small hardware memory bank used for special purposes.
• bump mapping

In computer graphics, a technique for simulating rough textures by creating irregularities in shading.
• byte

Common unit of computer storage (micro to mainframe). It is made up of eight binary digits (bits). A ninth bit may be added as a parity bit for error checking.
A byte holds the equivalent of a single character, such as the letter A, a dollar sign or decimal point. For numbers, a byte can hold a single decimal digit (0 to 9), two numeric digits (packed decimal) or a number from 0 to 255 (binary numbers).
Byte Specifications
The primary specifications of hardware are rated in bytes; for example, a 40-megabyte (40M or 40MB) disk holds 40 million characters of instructions and data. A one-megabyte (1M or 1MB) memory allows one million characters of instructions and data to be stored internally for processing.
With database files and word processing documents, the file size is slightly larger than the number of data characters stored in it. Word-processing files contain embedded codes for layout settings (margins, tabs, boldface); therefore, a100,000-byte document implies slightly less than 100,000 characters of text (approx. 30 pages). Database files contain codes that describe the structure of the records, thus, a 100,000-byte database file holds somewhat less than 100,000 characters of data.
Unlike data and text, a 100,000-byte graphics file is not indicative of the size of the image contained in it. There are many graphics standards, and the higher the image quality, the more bytes are needed to represent it. A low- resolution graphics file can take as little as 8,000 bytes, while high-resolution files can take 100,000 or more bytes per picture.
• CD-ROM

(Compact Disc Read Only Memory) A compact disc format used to hold text, graphics and hi-fi stereo sound. It's like an audio CD, but uses a different track format for data. The audio CD player cannot play CD-ROMs, but CD-ROM players usually play audio CDs and have output jacks for a headphone or amplified speakers.
CD-ROMs hold in excess of 650MB of data, which is equivalent to about 250,000 pages of text or 20,000 medium-resolution images.
• cold boot

Starting the computer by turning power on. Turning power off and then back on again clears memory and many internal settings. Some program failures will lock up the computer and require a cold boot to use the computer again. In other cases, only a warm boot is required. See warm boot and boot.
• color space

A 3-D model of the three attributes of a color, which are hue, value and saturation (chroma).
• contrast

The difference between the lightest and darkest areas on a display screen. Contrast with brightness.
• core storage.

Non-volatile memory that holds magnetic charges in ferrite cores about 1/16th" diameter. The direction of the flux determines the 0 or 1. Developed in the late 1940s by Jay W. Forrester and Dr. An Wang, it was used extensively in the 1950s and 1960s. Since it holds its content without power, it is still used in specialized applications in the military and in space vehicles.
• CPU

(Central Processing Unit) Computing part of the computer. Also called the processor, it is made up of the control unit and ALU.
A personal computer CPU is contained on a single microprocessor. A minicomputer CPU is contained on one or several printed circuit boards. A mainframe CPU is contained on many printed circuit boards.
The CPU, clock and main memory make up a computer. A complete computer system requires the addition of control units, input, output and storage devices and an operating system.
The terms CPU and processor imply the use of main memory as in the sentence "data is sent to the CPU and then processed," since the data must be stored in memory in order to be processed.
• CRT

(Cathode Ray Tube) A vacuum tube used as a display screen in a video terminal or TV. The term more often refers to the entire monitor rather than just the tube itself. Years ago, CRT was the popular term for the display screen. Today, monitor is the preferred term. See VGA and monitor.
• Cyberpunk

A futuristic, online delinquent: breaking into computer systems; surviving by high-tech wits. The term comes from science fiction novels such as "Neuromancer" and "Shockwave Rider."
• Cyberspace

Coined by William Gibson in his novel "Neuromancer," it is a futuristic computer network that people use by plugging their minds into it! The term is now used to refer to the Internet or to the online or digital world in general. See Internet and virtual reality.
• D/A converter

(Digital to Analog Converter) A device that converts digital pulses into analog signals. Contrast with A/D converter. See DSP and ladder DAC.
• database

A set of related files that is created and managed by a database management system (DBMS). Today, DBMSs can manage any form of data including text, images, sound and video. Database and file structures are always determined by the software. As far as the hardware is concerned, it's all bits and bytes.
• Defragment

To reorganize the disk by putting files into contiguous order. Because the operating system stores new data in whatever free space is available, data files become spread out across the disk if they are updated often. This causes extra read/write head movement to read them back. Periodically, the hard disk should be defragmented to put files back into order. See DOS Defrag.
• digit

A single character in a numbering system. In decimal, digits are 0 through 9. In binary, digits are 0 and 1.
• digital camera

A video camera that records its images in digital form. Unlike traditional analog cameras that convert light intensities into infinitely variable signals, digital cameras convert light intensities into discrete numbers. It breaks down the picture image into a fixed number of pixels (dots), tests each pixel for light intensity and converts the intensity into a number. In a color digital camera, three numbers are created, representing the amount of red, green and blue in each pixel.
Cameras used today for TV production are digital in design and record their initial field of view as a digital image, using charge coupled devices (CCDs). However, after a microprocessor processes the image, it is converted into analog form for recording on analog tape recorders. The analog method is still much more economical for routine video recording and playback. However, some day, it is expected that TV recording will be all digital from start to finish.
• digitize

To convert an image or signal into digital code by scanning, tracing on a graphics tablet or using an analog to digital conversion device. 3-D objects can be digitized by a device with a mechanical arm that is moved onto all the corners.
• DOS Copy Con

Internal command for creating a quick batch file. For example, to create the WRITE batch file, type: copy con: write.bat After pressing Enter, you'll get a blank line. Type your text and press Enter to end the line. When done, press F6 (ctrl-Z), then press Enter. Copy Con works a line at a time. You can't go back and change lines, but you can use backspace to delete characters on the same line.
• DOS

(1) (Disk Operating System) Pronounced "dawss." Generic term for operating system.
(2) (Disk Operating System) Single-user operating system for the PC, PS/1 and PS/2 series from IBM. DOS is also called PC-DOS to distinguish it from MS-DOS, the version for non-IBM PCs. DOS and MS- DOS are developed by Microsoft, are almost identical, and both are referred to as DOS. Over time, DOS development has been shared in varying degrees by IBM. See PC (Operating Environment).
• expansion slot

A receptacle inside a computer or other electronic system that accepts printed circuit boards. The number of slots determines future expansion. In personal computers, expansion slots are connected to the bus.
• flatbed scanner

A scanner that provides a flat, glass surface to hold pages of paper, books and other objects for scanning. The scan head is moved under the glass across the page. Sheet feeders are usually optionally available that allow multiple sheets to be fed automatically. Contrast with sheet-fed scanner, hand-held scanner and drum scanner.
• floppy disk

Reusable magnetic storage medium. It is the primary method for distributing personal computer software. It's also used to transfer data between users, although local area networks can eliminate much of this "sneakernet." Also called a diskette, the floppy is a flexible disk, similar to tape, with both surfaces used for magnetic recording. The disk drive grabs the floppy's center and spins it inside its housing, and the read/write head makes contact with the surface through an opening in the floppy's envelope, case or cartridge. Floppies are much slower than hard disks, because they spin at 300 rpm, a tenth the rotation of a hard disk, and they are at rest until a data transfer is requested. Although floppy disks look the same, what's recorded on them determines their capacity and compatibility. Each new floppy must be "formatted," which records the sectors on the disk that will hold the data. PC, Mac, Apple II, Amiga and Atari formats are different, although most can read and write PC (DOS) diskettes. See format program, Floptical and magnetic disk.
• format program

Software that initializes a disk. There are two formatting levels. The low-level initializes the disk surface by creating the physical tracks and storing sector identification in them. Low-level format programs are geared to the drive technology used (IDE, SCSI, etc.). The high-level format lays out the indexes used by the operating system (Mac, DOS, etc.) to keep track of data stored in the sectors. Floppy disk format programs perform both levels on a diskette. See DOS Format.
• fractals

A lossy compression method used for color images. It provides ratios of 100:1 or greater and is especially suited to natural objects, such as trees, clouds and rivers. It turns an image into a set of data and an algorithm for expanding it back to the original.
The term comes from "fractus," which is Latin for broken or fragmented. It was coined by IBM Fellow and doctor of mathematics Benoit Mandelbrot, who expanded on ideas from earlier mathematicians and discovered similarities in chaotic and random events and shapes.
• frame buffer

An area of memory used to hold a frame of data. A frame buffer is typically used for screen display and is the size of the maximum image area on screen. It is a separate memory bank on the display adapter that holds the bitmapped image while it is being "painted" on screen. Sophisticated graphics systems are built with several memory planes, each holding one or more bits of the pixel.
• full-motion video

Video transmission that changes the image 30 frames per second (30 fps). Motion pictures are run at 24 fps, which is the minimum frequency required to eliminate the perception of moving frames and make the images appear visually fluid to the eye.
TV video generates 30 interlaced frames per second, which is actually transmitted as 60 half frames per second.
Video that has been digitized and stored in the computer can be displayed at varying frame rates, depending on the speed of the computer. The slower the computer, the more jerky the movement. Contrast with freeze-frame video.
• function keys

A set of keyboard keys used to command the computer (F1, F2, etc.). F1 is often the help key, but the purpose of any function key is determined by the software currently running.
• GIF

(Graphics Interchange Format) A popular raster graphics file format developed by CompuServe that handles 8-bit color (256 colors) and uses the LZW method to achieve compression ratios of approximately 1.5:1 to 2:1.
GIF files include a color table which includes the most representative 256 colors used in the image. For example, a picture of the forest would include a color table with mostly greens. This method provides excellent realism in an 8-bit image. In addition, GIF file sizes are based on the actual number of colors used. Thus images with fewer colors take up less space in the computer.
GIF89 is a more sophisticated version of GIF87 and allows one of the colors to be made transparent, taking on the background color of the underlying page or window.
• Gouraud shading

In computer graphics, a technique developed by Henri Gouraud that computes a shaded surface based on the color and illumination at the corners of polygonal facets.
• graphics

Called computer graphics, it is the creation and manipulation of picture images in the computer. It is defined here as graphics, to keep it next to the other entries that begin with "graphics."
A graphics computer system requires a graphics display screen, a graphics input device (tablet, mouse, scanner, camera, etc.), a graphics output device (dot matrix printer, laser printer, plotter, etc.) and a graphics software package; for example, a CAD, drawing or paint program.
• GUI

(Graphical User Interface) A graphics-based user interface that incorporates icons, pull-down menus and a mouse. The GUI has become the standard way users interact with a computer. The three major GUIs are Windows, Macintosh and Motif. In a client/server environment, the GUI resides in the user's client machine. See desktop manager, window manager and Star. Contrast with CUI.
• halftone

In printing, the simulation of a continuous-tone image (shaded drawing, photograph) with dots. All printing processes, except for Cycolor, print dots. In photographically-generated halftones, a camera shoots the image through a halftone screen, creating smaller dots for lighter areas and larger dots for darker areas. Digitally-composed printing prints only one size of dot.
In order to simulate varying size halftone dots in computer printers, dithering is used, which creates clusters of dots in a "halftone cell." The more dots printed in the cell, the darker the gray. As the screen frequency gets higher (more lines per inch), there is less room for dots in the cell, reducing the number of gray levels that can be generated.
• hard copy

Printed output. Contrast with soft copy.
• hard disk

Primary computer storage medium that is made of rigid disks with a magnetic recording surface. Personal computer hard disks hold from 20MB to over 1GB. Mini and mainframe hard disks can hold several gigabytes. Fixed hard disks are permanently sealed in the drive. Removable hard disks are encased in disk pack or disk cartridge modules that can be moved between computers with the same kinds of drives. Hard disks provide fast retrieval because they rotate at 3,600 rpm and higher and spin constantly, although laptops turn them off to preserve battery. Hard disks are made of one or more aluminum platters (two to 15" diameter), each side coated with a ferromagnetic material. Hard disks are usually low-level formatted from the factory, which records the original sector identification on them. See floppy disk, magnetic disk and format program.
• hardware

All machinery and equipment. Contrast with software, which is a set of instructions that tell the computer what to do. Also contrast with data, which are the facts and figures that are stored in the hardware and controlled by software.
Hardware vs. Software
In operation, a computer is both hardware and software. One is useless without the other, and each rules the other. The hardware design specifies what instructions it can follow, and the instructions then tell it what to do.
As inseparable as hardware and software are in operation, they are quite different when they are being evaluated. Hardware is the world of storage and transmission. Software is the world of logic and language.
The more memory and disk storage a computer system has, the more work it can do. The faster the memory and disks transmit data and instructions between them and the CPU, the faster the work gets done. A user's problem can be translated into a hardware requirement based on the size of the files and databases that will be created and the number of concurrent users at terminals.
Software, on the other hand, is harder to specify. The programs must process the organization's business transactions properly, and even the smallest company can have complicated transactions.
Hardware always deals with the data processing problem the same way. How much? How fast? But software deals with the tedious details of an ever- changing business. It's much harder to analyze, design and develop the software solution than it is to specify the hardware.
• high color

The ability to generate 32,768 colors (15 bits) or 65,536 colors (16-bit). 15-bit color uses five bits for each red, green and blue pixel. The 16th bit may be a color, such as XGA with 5-red, 6-green and 5-blue, or be an overlay bit that selects pixels to display over video input. See true color.
• high-level language

Machine-independent programming language, such as FORTRAN, COBOL, BASIC, Pascal and C. It lets the programmer concentrate on the logic of the problem to be solved rather than the intricacies of the machine architecture such as is required with low- level assembly languages.
• home page

A foundation, or starting, page on the World Wide Web. Home pages are used as tables of contents and indexes to other resources on the Web or to other Internet servers. See World Wide Web and URL.
• HotJava

A Web browser from Sun Microsystems that supports the Java programming language, also developed by Sun. HotJava executes Java programs embedded directly within Web documents.
• HTML

(HyperText Markup Language) A standard for defining documents with hypertext links. HTML is a subset of SGML (Standard Generalized Markup Language) and is used to establish links between documents on the World Wide Web.
• hue

In computer graphics, a particular shade or tint of a given color.
• hypermedia

The use of data, text, graphics, video and voice as elements in a hypertext system. All the various forms of information are linked together so that a user can easily move from one to another.
• hypertext

A linkage between related text. For example, by selecting a word in a sentence, information about that word is retrieved if it exists, or the next occurrence of the word is found. The concept was coined by Ted Nelson as a method for making the computer respond to the way humans think and require information. In the electronic versions of this database, you can hypertext to the definition of any term used within the definitions by clicking on it or highlighting it with the mouse.
• I/O

(Input/Output). Transferring data between the CPU and a peripheral device. Every transfer is an output from one device and an input into another.
• image editing

Changing or improving graphics images either interactively using a paint program or by using software routines that alter contrast, smooth lines or filter out unwanted data. See image filter and anti-aliasing.
• image processing

(1) The analysis of a picture using techniques that can identify shades, colors and relationships that cannot be perceived by the human eye. It is used to solve identification problems, such as in forensic medicine or in creating weather maps from satellite pictures and deals with images in raster graphics format that have been scanned in or captured with digital cameras. (2) Any image improvement, such as refining a picture in a paint program that has been scanned or entered from a video source. (3) Same as imaging.
• interactive

Back-and-forth dialog between the user and a computer.
• interface

Connection and interaction between hardware, software and the user. Hardware interfaces are the plugs, sockets and wires that carry electrical signals in a prescribed order. Software interfaces are the languages, codes and messages that programs use to communicate with each other, such as between an application program and the operating system. User interfaces are the keyboards, mice, dialogues, command languages and menus used for communication between the user and the computer.
Interfacing is a major part of what engineers, programmers and consultants do. Users "talk to" the software. The software "talks to" the hardware, as well as to other software. Hardware "talks to" other hardware. All this "talking to" is interfacing. It has to be designed, developed, tested and redesigned, and with each incarnation, a new specification is born that may become a de facto standard or a regulated standard.
• internet access provider

An organization that provides access to the Internet. Dial-up customers are billed a fixed rate per month or by hourly usage or both. The major online services (CompuServe, America Online, etc.) have all become Internet access providers. Access providers may also offer leased line services for companies that want dedicated high-speed access to the Internet (56Kbps, T1, etc.). See PDIAL.
• internet

(1) A large network made up of a number of smaller networks. (2) (Internet) "The" Internet is made up of more than 40,000 interconnected networks in over 70 countries, comprised of academic, commercial, government and military networks. Originally developed for the military, the Internet became widely used for academic and commercial research. Users have access to unpublished data, journals and BBSs for every subject known to humankind. Today, the Internet is being commercialized into a worldwide information highway.
The recent surge in growth is twofold. As the major online services (CompuServe, America Online, etc.) connected to the Internet for e-mail exchange, the Internet began to function as a central hub for e-mail outside of the Internet community. A member of one online service could now send mail to a member of another online service using the Internet as a gateway. It has glued the world together for electronic mail.
Secondly, the World Wide Web facility on the Internet links documents around the world, providing an information exchange of unprecedented proportion. With the advent of Web browsers such as Mosaic and NetScape Navigator, this wealth of information has been made easily available to users with PCs and Macs rather than only scientists and hackers at UNIX workstations. Today, the online services also provide full Internet access. DELPHI was the first, and all the others followed suit. Now you can download files from the Internet and access the World Wide Web via your online account. In addition, independent Internet access providers have seemingly risen out of the woodwork to offer individuals and organizations access to the Internet. Many have been overwhelmed by the flood of business, which often results in too many busy signals when trying to log on and poor customer support.
The backbone of the Internet is a series of high-speed communications links between major supercomputer sites and educational and research institutions within the U.S. and throughout the world. The U.S. National Science Foundation maintains a major part of the backbone, called the NSFNET. The access providers hook into the backbone and provide lines for subscribers. Internet computers use the TCP/IP communications protocol. There are over two million hosts on the Internet, a host being a mainframe, mini or workstation that directly supports the Internet Protocol (the IP in TCP/IP). The Internet is connected to all types of computer networks worldwide via gateways that convert TCP/IP into other protocols.
Some of the major utilities used to work the Internet are FTP, Archie, Telnet, Gopher and Veronica. FTP stands for File Transfer Protocol. There are countless files throughout the Internet that can be downloaded free of charge using FTP. Archie is a utility that provides listings of these files. Telnet is a terminal emulation program that lets you log onto a computer in the Internet and run a program. Gopher is a utility that lets you search hierarchical menus describing Internet files (not just file names), and Veronica lets you make more sophisticated searches on Gopher sites. See FTP, Archie, Telnet, Gopher and Veronica.
The IAB, or Internet Activities Board is the governing body for the Internet. Its Internet Research Task Force (IRTF) explores new technologies which it refers to the Internet Engineering Task Force (IETF). The IETF works on the specifications of new standards. To obtain a list of organizations that provide access to the Internet, see PDIAL. For a list of World Wide Web sites, see Yahoo. See Lessons Internet, information superhighway and online services. Is It Going Commercial? There is more activity, excitement and hype about the Internet than ever. Using the World Wide Web, thousands of companies, from conglomerates to mom and pop shops, are contemplating how to make the Internet a worldwide shopping mall. Will it succeed? Will it be too confusing? Will Internet traffic bog down like the Los Angeles freeway? Stay tuned! Getting Started? For a list of good books on the Internet, see Internet references.
• Java

A programming language for World Wide Web applications from Sun Microsystems. Java was modeled after C++, and Java programs are embedded into HTML documents. The first Web browsers to run Java applications are Sun's HotJava and Netscape's Navigator 2.0.
• JPEG

(Joint Photographic Experts Group) An ISO/ITU standard for compressing still images that is becoming very popular due to its high compression capability. Using discrete cosine transform, it provides lossy compression (you lose some data from the original image) with ratios up to 100:1 and higher. It depends on the image, but ratios of 10:1 to 20:1 may provide little noticeable loss. The more the loss can be tolerated, the more the image can be compressed. Compression is achieved by dividing the picture into tiny pixel blocks, which are halved over and over until the ratio is achieved.
JPEG is implemented in software and hardware, with the latter providing sufficient speed for realtime, on-the-fly compression. C-Cube Microsystems introduced the first JPEG chip. JPEG++ is an extension to JPEG from Storm Technology, Mountain View, CA, that allows picture areas to be selectable for different ratios. For example, the background could be compressed higher than the foreground image. JPEG uses the JPEG File Interchange Format, or JFIF. File extensions are .JPG or .JFF. M-JPEG and MPEG are variations of JPEG used for full-motion digital video. See MPEG.
• kerning

In proportional spacing, the tightening of space between letters to create a visually appealing flow to the text. Letter combinations, such as WA, MW and TA, are routinely kerned for better appearance. See tracking.
• keyframe. animation

Animating a graphics object by creating smooth transitions between various
• keyframe

In computer graphics animation, a frame that indicates the beginning or end of an object in motion. kiosk
A small, self-standing structure such as a newstand or ticket booth. Unattended multimedia kiosks dispense public information via computer screens. Either a keyboard, touch screen or both are used for input.
• LaserDisc

A 12" diameter optical disk used for full-motion video. Various videodisc systems were introduced in the 1970s, but only LaserVision from Philips survived. LaserDiscs have been used for interactive training as well as for home theater, where its superior resolution is noticeable on larger screens. However, for the most part, CD-ROMs have replaced LaserDiscs for training, and it is expected that DVDs will replace the LaserDisc for movies. Movies use the CLV (constant linear velocity) format, which records the signal on a continuous, spiraling track. Each side contains 108,000 frames and one hour of video. The signal density is uniform, and the player varies the speed of the disc. For fast direct access for interactive training and games, the CAV (constant angular velocity) format is used. Tracks are concentric circles, each containing one video frame. There are 54,000 frames and 30 minutes of video per side. Early LaserDiscs recorded analog sound. Today, most LaserDiscs contain analog and digital soundtracks, and newer players default to the digital sound if available. Some players let the user select the soundtrack, allowing multiple languages and other annotations to be included on the same disc.
• linear video editing

Editing analog videotape. Before digital editing (nonlinear video editing), video sequences were edited by inserting new frames and reconstructing the balance of the tape by adding the remainder of the frames. Contrast with nonlinear video editing.
• lossless compression

Compression techniques that decompress data 100% back to original. Contrast with lossy compression.
• lossy compression

Compression techniques that does not decompress data 100% back to original. Images and audio samples may be able to afford small losses of resolution in order to increase compression. Contrast with lossless compression.
• low-level language

Programming language that is very close to machine language. All assembly languages are low-level languages. Contrast with high-level language.
• luminance

The amount of brightness, measured in lumens, that is given off by a pixel or area on a screen. It is the black/gray/white information in a video signal.
• MB, Mb

(1) (M "upper case B") (MegaByte or MotherBoard) MB mostly stands for megabyte, but on ads for raw components, it may refer to motherboard. (2) (M "lower case b") (MegaBit) Mb should stand for megabit, but adherence to lower case "b" for bit is not always followed. Mb often refers to megabyte. See space/time for common usage.
• Mbone

(Multicast backBONE) A collection of sites on the Internet that support the IP multicasting protocol (one-to-many) and allow for live audio and videoconferencing.
• memory

The computer's workspace (physically, a collection of RAM chips). It is an important resource, since it determines the size and number of programs that can be run at the same time, as well as the amount of data that can be processed instantly.
All program execution and data processing takes place in memory. The program's instructions are copied into memory from disk or tape and then extracted from memory into the control unit circuit for analysis and execution. The instructions direct the computer to input data into memory from a keyboard, disk, tape or communications channel. As data is entered into memory, the previous contents of that space are lost. Once the data is in memory, it can be processed (calculated, compared and copied). The results are sent to a screen, printer, disk, tape or communications channel. Memory is like an electronic checkerboard, with each square holding one byte of data or instruction. Each square has a separate address like a post office box and can be manipulated independently. As a result, the computer can break apart programs into instructions for execution and data records into fields for processing.
Memory Doesn't Usually Remember Oddly enough, the computer's memory doesn't remember anything when the power is turned off. That's why you have to save your files before you quit your program. Although there are memory chips that do hold their content permanently (ROMs, PROMs, EPROMs, etc.), they're used for internal control purposes and not for the user's data. "Remembering" memory in a computer system is its disks and tapes, and although they are also called memory devices, many prefer to call them storage devices (as we do) in order to differentiate them from internal memory. Perhaps in time, memory will refer to disks exclusively and RAM will refer to working memory. Until then, its usage for both RAM and disk only adds confusion to the most confusing industry on earth.
Memory Can Get Clobbered! Memory is such an important resource that it cannot be wasted. It must be allocated by the operating system as well as applications and then released when not needed. Errant programs can grab memory and not let go of it even when they are closed, which results in less and less memory available as you load and use more programs. In addition, if the operating system is not advanced, a malfunctioning application can write into memory used by another program, causing all kinds of unspecified behavior. You discover it when the system freezes or something wierd happens all of a sudden. If you were to really look into memory and watch how much and how fast data and instructions are written into and out of it in the course of a day, it's truly a miracle that it works. Other terms for memory are RAM, main memory, main storage, primary storage, read/write memory, core and core storage.
• menu

List of available options on screen. Selection is accomplished by highlighting the option with a mouse or cursor keys and clicking the mouse or pressing Enter. See Lotus menu and pull-down menu.
• microcomputer

Same as personal computer.
• minicomputer

Small to medium-scale computer that functions as a single workstation, or as a multi-user system with up to several hundred terminals. A minicomputer system costs roughly from $20,000 to $250,000.
In 1959, Digital launched the minicomputer industry with its PDP-1. Soon after, Data General and HP introduced minicomputers, and eventually Wang, Tandem, Datapoint and Prime joined them. IBM has introduced several minicomputer series, including the System/34, System/36, System/38, Series/1, 8100 and AS/400. See supermini.
Since high-end microcomputers and low-end mainframes offer price and performance in the traditional minicomputer niche, the term is beginning to have less significance. Some companies are replacing this term with small, medium and large-scale designations. Also, the term midrange is becoming popular for this size of computer.
• modeling

Simulating a condition or activity by performing a set of equations on a set of data. See data model, data administration, financial planning system and scientific applications.
• modem

(MOdulator-DEModulator) A device that adapts a terminal or computer to a telephone line. It converts the computer's digital pulses into audio frequencies (analog) for the telephone system and converts the frequencies back into pulses at the receiving side. The modem also dials the line, answers the call and controls transmission speed, which ranges from 300 to 14,400 bps and higher.
• motion path

In computer graphics, the path to be followed by an animated object.
• motion video

Refers to moving video images, but does not imply a frame rate. Full-motion video refers to fluid, TV-like images displayed at a rate of 24 to 30 frames per second.
• MPEG

(Moving Pictures Experts Group) An ISO/ITU standard for compressing video. MPEG-1, which is used in CD-ROMs and Video CDs, provides a resolution of 352x240 at 30 fps with 24-bit color and CD-quality sound. Some MPEG boards can also magnify the image to full screen. MPEG-2 is a full-screen video standard used in upcoming DVD media that hold significantly more data than current-day CDs. MPEG is a lossy method. MPEG uses the same intraframe coding as JPEG for individual frames, but also uses interframe coding, which further compresses the video data by encoding only the differences between periodic key frames, known as I-frames. A variation of MPEG, known as Motion JPEG, or M-JPEG, does not use interframe coding and is thus easier to edit in a nonlinear editing system than full MPEG. For effective playback, MPEG-encoded material requires either a fast computer (Pentium, PowerPC, etc.) or a plug-in MPEG board such as Sigma Designs' RealMagic. It is expected that MPEG circuits will be built into future computers. See JPEG.
• MUD

(MultiUser Dungeons) Games that are played by multiple users on the Internet, using the Internet Relay Chat (IRC). MUD also stands for multiuser dialogues. A companion to MUDs are MUSEs, which stand for multiuser simulation environments or multiuser shared environments. multicast To transmit a message to multiple recipents at the same time. Multicasting is used in teleconferencing and data communications networks. Multicast is a one-to-many transmission that implies sending to several designated recipients, whereas broadcast implies sending to everyone connected to the network. Contrast with unicast. OpenGL (OPEN Graphics Language) A 3-D graphics language developed by Silicon Graphics and endorsed by a variety of vendors. Windows NT Version 3.5 supports
• OpenGL

(OPEN Graphics Language) A 3-D graphics language developed by Silicon Graphics and endorsed by a variety of vendors. Windows NT Version 3.5 supports OpenGL.
• output device

Any peripheral that presents output from the computer, such as a screen or printer. Although disks and tapes receive output, they are called storage devices.
• operating system

Master control program that runs the computer and acts as a scheduler and traffic cop. It is the first program loaded into the computer when it is turned on, and the central part of the operating system, called the kernel, resides in memory at all times. It may be developed by the vendor of the computer it's running in or by a third party.
It is an important component of the computer system, because it sets the standards for the application programs that run in it. All programs must be written to "talk to" the operating system.
Also called an executive or supervisor, the operating system performs the following functions.
Job Management
In small computers, the operating system responds to commands from the user and loads the requested application program into memory for execution. In large computers, the operating system carries out its job control instructions (JCL), which describe the programs that must be run for an entire shift.
Task Management
In single tasking computers, the operating system has virtually no task management to do, but in multitasking computers, it is responsible for the concurrent operation of one or more programs (jobs). Advanced operating systems have the ability to prioritize programs so that one job gets done before the other.
In order to provide users at terminals with the fastest response time, batch programs can be put on lowest priority and interactive programs can be given highest priority. Advanced operating systems have fine-tuning capabilities so that a specific job can be speeded up or slowed down by commands from the computer operator.
Multitasking is accomplished by designing the computer to allow instructions to be executed during the same time data is coming into or going out of the computer. In the seconds it takes one user to type in data, millions of instructions can be executed for dozens, or even hundreds, of other users. In the milliseconds it takes for data to come in from or go out to the disk, thousands of instructions can be performed for some other task.
Data Management
A major function of an operating system is to keep track of data on disk; hence the term DOS, or disk operating system. The application program does not know where the data is actually stored or how to get it. That knowledge is contained in the operating system's access method, or device driver, routines. When a program is ready to accept data, it signals the operating system with a coded message. The operating system finds the data and delivers it to the program. Conversely, when the program is ready to output, the operating system transfers the data from the program onto the available space on disk.
Device Management
In theory, the operating system is supposed to manage all devices, not just disk drives. It is supposed to handle the input and output to the display screen as well as the printer. By keeping the details of the peripheral device within the operating system, a device can be replaced with a newer model, and only the routine in the operating system that deals with that device needs to be replaced.
In the PC world running DOS, software developers often bypass the operating system, because DOS either doesn't support the device or adds too much performance overhead. For example, developers with graphics, word processing and desktop publishing applications have become responsible for providing drivers (routines) for all the popular displays and printers, adding an enormous burden to their development efforts.
Security
Multi-user operating systems maintain a list of authorized users and provide password protection to unauthorized users who may try to gain access to the system. Large operating systems also maintain activity logs and accounting of the user's time for billing purposes. They also provide backup and recovery routines to start over again in the event of a system failure.
History
The earliest operating systems were developed in the late 1950s to manage tape and disk storage, but programmers often felt more comfortable writing their own I/O routines. In the mid 1960s, operating systems became essential to manage the complexity of timesharing and multitasking.
Today, all multi-purpose computers from micro to mainframe use an operating system. Special-purpose devices (appliances, games, toys, etc.) do not. They usually employ a single program that performs all the required I/O and processing tasks.
Common Operating Systems
PCs use DOS, OS/2, SCO XENIX and AIX. Apple II's use ProDOS. Macintoshes use the System along with Finder and Multifinder, as well as A/UX. Digital uses VMS and Ultrix. IBM mainframes use MVS, VM and VSE.
In the past, when a vendor introduced a new operating system, users had little understanding of this behind-the-glass-enclosed-data center phenomenon. Today, it is squarely in their hands.
Perhaps the Japanese have the right idea with their TRON operating system. It is intended to be a common interface across all applications from a microwave oven to the largest supercomputer!
• parallel port

A socket on a computer used to connect a printer or other peripheral device. It may also be used to attach a portable hard disk, tape backup or CD-ROM. Transferring files between two PCs can be accomplished by cabling the parallel ports of both machines together and using a file transfer program such as LapLink. On the back of a PC, the parallel port is a 25-pin female DB-25 connector. In a PC, the parallel port circuit is contained on a small expansion card that plugs into an expansion slot. Typically two serial ports, one parallel port and one game port are on the card. These ports are often also included on an IDE host adapter card, which takes up only one expansion slot and provides hard and floppy disk control as well as I/O. The Enhanced Parallel Port, or EPP, is a higher-speed parallel port standard that has been sanctioned by the IEEE. The EPP is expected to become widely used on PCs. See IEEE 1284.
• PARC

(Palo Alto Research Center) Xerox's research and development center where the Smalltalk programming language and GUI interface were developed. Established in 1970, it is located in the Stanford University Industrial Park, Palo Alto, CA.
• peripheral

Any hardware device connected to a computer, such as a monitor, keyboard, printer, plotter, disk or tape drive, graphics tablet, scanner, joy stick, paddle and mouse.
• personal computer

Synonymous with microcomputer, a computer that is functionally similar to larger computers, but serves only one user. It is used at home and in the office for almost all applications traditionally performed on larger computers.
With the addition of a modem, a personal computer becomes a terminal to the outside world, capable of retrieving information from other computers and information utilities.
There are a wide variety of personal computers on the market, priced from $300 to over $10,000. The size of the computer is based on its memory and disk capacity. Its speed is based on the CPU that runs it, and its visual quality is based on the resolution of its display screen and printer.
Most personal computers run one program at a time, but multitasking machines, which run more than one program concurrently, will become more common in the 1990s.
MAJOR SUPPLIERS OF PERSONAL COMPUTERS
The personal computer world is overwhelmingly dominated by IBM PCs and IBM-compatible PCs. There are hundreds of vendors and thousands of models to choose from, although all models fall into a handful of categories (see PC).
The next largest supplier is Apple Computer, which provides the Apple II and Macintosh families. The Apple II series is the most widely used computer in elementary and high schools as well as at home. The Macintoshes are popular with small businesses and are increasingly being purchased by large corporations.
Both Atari and Commodore continue to carve out a niche and are popular as home and small business computers. Each of them has support from software vendors providing a rounded supply of applications.
THE HISTORY OF PERSONAL COMPUTERS The personal computer industry began in 1977, when Apple, Radio Shack and Commodore introduced the first off-the-shelf computers as consumer products.
The first machines used an 8-bit microprocessor with a maximum of 64K of memory and floppy disks for storage. The Apple II, Atari 500, and Commodore 64 became popular home computers, and Apple was successful in the business market after the VisiCalc spreadsheet was introduced. However, the business world was soon dominated by the Z80 processor and CP/M operating system. It was used by countless vendors in the early 1980s, such as Vector Graphic, NorthStar, Osborne and Kaypro. By 1983, hard disks began to show up on these machines, but CP/M was soon to be history.
In 1981, IBM introduced the PC, an Intel 8088- based machine, slightly faster than the genre, but with 10 times the memory. It was floppy-based, and its DOS operating system from Microsoft was also available for the clone makers (MS-DOS). The 8088 was cleverly chosen so that CP/M software vendors could convert to it easily. They did!
dBASE II was introduced in 1981 bringing mainframe database functions to the personal computer level and launching an entire industry of compatible products and add-ons.
Lotus 1-2-3 was introduced in 1982, and its refined interface and combined graphics helped spur sales of the new IBM standard.
The IBM PC was successfully cloned by Compaq and unsuccessfully cloned by others. However, by the time IBM announced the AT in 1984, vendors were effectively cloning the PC and, as a group, eventually succeeded in grabbing the majority of the PC market.
In 1983, Apple introduced the Lisa, a graphics- based machine that simulated the user's desktop. Lisa was way ahead of its time, but Apple abandoned it for the Macintosh in 1984. The graphics-based desktop environment caught on with the Mac, especially in desktop publishing, and the graphical interface, or "gooey," (GUI) worked its way to the PC world with Microsoft Windows, and, eventually Ventura Publisher with its GEM interface.
In 1986, the Compaq 386 ushered in the first Intel 80386-based machine. In 1987, IBM introduced the PS/2, its next generation of personal computers, which added improved graphics, 3.5" floppy disks and an incompatible bus to help fend off the cloners. OS/2, jointly developed by IBM and Microsoft, was also introduced to effectively handle the new, larger machines, but it has been slow to catch on.
In the same year, more powerful Macintoshes were introduced, including the Mac SE and Mac II, which have opened new doors for Apple.
In 1989, IBM and compatible vendors introduced 80486-based computers, and faster Macintoshes were also introduced.
Inspired by Radio Shack's Model 100 in 1984 and ignited by Toshiba and Zenith, the laptop market provides one of the most fascinating growth areas in personal computing. More and more power is being stuffed into less and less space, providing computing power on the go that few would have imagined back in 1977.
THE FUTURE
The personal computer industry sprang up without any cohesive planning. All of a sudden, it was there, and individual machines were bought to solve individual problems, such as automating a budget, typing a letter or searching a file.
However, in large organizations, the real data exists in the mainframe, and it doesn't serve the organization to have an employee retype the mainframe reports into the micro in order to analyze and manipulate it.
The personal computer, originally out of the control of IS professionals, is now back in their hands. Personal computers can serve as invaluable tools for the user when they are designed into the fabric of the organization. The major issue of the 1990s will be to tie them together in local area networks and to interconnect them with the organization's minis and mainframes.
The new, fast personal computers (Intel 386, 486, Motorola 68030, 68040, etc.) are changing the marketplace. Not only do they begin to compete with minicomputer workstations, but, as we enter the 1990s, networks of these machines will be installed for applications that were previously relegated to minis and mainframes.
These high-powered desktop computers will encourage the development of more artificial intelligence applications that are the backbone of the next computing generation. By the turn of the century, you should be able to talk to your computer as easily as typing on it.
As standalone machines, personal computers have placed creative capacity into the hands of an individual that would have cost millions of dollars less than 20 years ago. Its use is slowly but surely shifting the balance of power from the large company to the small company, from the elite to the masses, from the wealthy to individuals of modest means. In little more than a decade, the personal computer has revolutionized the computer industry and the world.
• Phong Shading

In 3-D graphics, a technique developed by Phong Bui Tuong that computes a shaded surface based on the color and illumination at each pixel. The surface normals at the triangle's points are used to compute a surface normal for each pixel, which in turn creates a more accurate RGB value for each pixel. Phong shading is more realistic than Gouraud shading, but requires much more computation. See Gouraud shading.
• Photo CD

A CD imaging system from Kodak that digitizes 35mm slides or negatives onto a CD-ROM disc. The Photo CD is created by photo finishers that have a Kodak Picture Imaging Workstation. It takes about a half hour to put 100 photos (the maximum per disc) onto the CD. Each photographic-quality image (2048x3072x24) compresses into six megabytes. A replica of each image in the form of contact prints is also included. The minimum RAM required is 4MB, but 10MB is needed in order to display an image in full resolution. Hardware requirements for Photo CDs are a CD-ROM drive that conforms to the CD-ROM XA standard. Earlier CD-ROM drives are single session drives, which can only read the original set of images recorded on the disc. A multisession drive is required to read Photo CD images that were added after the original set. Most new CD-ROM drives provide multisession capability. Other formats include the Photo CD Portfolio, which holds up to 800 TV-quality images (512x768), the Pro Photo CD, which stores images from professional format film (120, 4x5, etc.), the Photo CD Catalog, which holds thousands of pictures and the Photo CD Medical disk for storing film-based images. There are a variety of software packages that access Photo CD images, and increasingly, paint, drawing and image enhancement programs are importing the Photo CD format (PCD file). A Kodak Photo CD player is available that lets you view the Photo CDs on your TV and also play audio CDs.
• PICT

(PICTure) A Macintosh graphics file format that stores images in the QuickDraw vector format. The PICT2 format can also include gray-scale bitmapped images. When PICT files are converted to the PC, they use the .PCT file extension.
• pixel

(PIX [picture] ELement) Smallest element on a video display screen. A screen is broken up into thousands of tiny dots, and a pixel is one or more dots that are treated as a unit. A pixel can be one dot on a monochrome screen, three dots (red, green and blue) on color screens, or clusters of these dots.
For monochrome screens, the pixel, normally dark, is energized to different light intensities, creating a range from dark to light. For color, each red, green and blue dot is energized to different intensities, creating a range of colors perceived as the mixture of these dots. Black is all three dots off, white is all three dots on, and grays are even intensities of each color.
The number of bits assigned to each pixel in its associated digital memory determines the number of shades and colors that can be represented. The most economical system is monochrome in which one bit is used per pixel (on or off). In the most elaborate color displays, which use up to four full bytes for each of the red, green and blue dots, each pixel can display billions of different shades. Considering that a high-resolution screen may use a million pixels, many megabytes of memory would have to be reserved to hold such an image.
• polygon

In computer graphics, a multi-sided object that can be filled with color or moved around as a single entity. polyhedron A six- or more-sided object. A group of connected polygons.
• polyline

In computer graphics, a single entity that is made up of a series of connected lines.
• PostScript

A page description language from Adobe Systems, Inc., Mountain View, CA, that is used extensively on Macs and PCs as well as workstations, minis and mainframes. It is the de facto standard in commercial typesetting and printing houses. Most all accept and may even require PostScript files as electronic input. PostScript commands do not drive the printer directly. They are language statements in ASCII text that are translated into the printer's machine language by a PostScript interpreter built into the printer. Fonts are scaled to size by the interpreter, thus eliminating the need to store a variety of font sizes on disk. PostScript Level 2, downward compatible with original PostScript, adds data compression and enhancements, especially for color printing. PostScript fonts come in Type 1 and Type 3 formats, and Adobe makes only Type 1. Type 1 fonts are widely used and are made by other companies as Adobe later made the format public. Type 1 fonts are encrypted and compressed and also allow for hints, which improve the appearance of text at 300 dpi and lower resolutions. Type 1 fonts use a simpler, more efficient command language than Type 3. With Adobe Type Manager, Type 1 fonts can also be used on non-PostScript printers. See Adobe Type Manager. Type 3 fonts do not use encryption or hints, but can use the entire PostScript language to create complex designs. They can also be bitmaps. Type 3 fonts are not widely used; however, in order to speed up printing small fonts on PostScript printers, Windows 3.1 creates Type 3 bitmaps from its TrueType outlines. Type 1 Font Files
Type 1 fonts are distributed by Adobe as two files. One contains the outlines, and the other contains the font metrics, which includes character widths and heights and kerning values. Type 1 font distribution disks for Windows contain PFB, AFM and INF files. The PFB (Printer Font Binary) outline files are copied to the hard disk, and the AFM (Adobe Font Metric) files are converted into PFM (Printer Font Metric) files on the hard disk. INF files contain information that the font installer requires. A font generator, called Font Foundry, is available from Adobe that converts Type 1 outlines into bitmaps for HP printers (.SFP and .SFL files) and screen fonts for DOS applications, such as WordPerfect and the GEM version of Ventura Publisher. Type 1 font distribution disks for the Mac contain outline and metric files that are copied onto the hard disk. For example, a Helvetica font would have an outline file named "Helve" and a font metrics file named "Helvetica." The icon for the font metrics file looks like a suitcase, and is often called the "suitcase file." A Helve.AFM file may also be included on the distribution disk. PostScript font distribution disks for UNIX contain both AFM and PFA (Printer Font ASCII) files. The PFA files contain the PostScript ASCII code of the outline.
• power supply

Electrical system that converts AC current from the wall outlet into the DC currents required by the computer circuitry.
• prepress

In typography and printing, the preparation of camera-ready materials up to the actual printing stage, which includes typesetting and page makeup. presentation graphics Presentation materials for overheads, 35mm slide shows and computer-driven slide shows (screen shows). Presentation graphics programs provide a wide selection of predefined backgrounds and page layouts as well as the ability to create various types of business graphics for charting numerical data. They include drawing and painting tools and the ability to select from stock graphical elements to illustrate a page. For computer-driven slide shows, the application provides a variety of special effects that can be used to fade and wipe one frame into another such as commonly found in the video world. Sound and video can also be merged into the presentation. Examples of Windows presentation graphics programs are Harvard Graphics, Freelance Graphics, PowerPoint and Charisma.
• Quicktime VR

The virtual reality version of QuickTime. It allows subjects to be viewed on screen in 3-D space. Scenes are compiled from renderings or from multiple still shots taken of all sides.
• QuickTime

Multimedia extensions to Macintosh's System 7 that add sound and video capabilities. A QuickTime file can contain up to 32 tracks of audio, video, MIDI or other time-based control information. Most major Macintosh DBMSs (database management systems) support QuickTime. Apple also provides a QuickTime for Windows version for Windows-based PCs.
• RAM

(Random Access Memory) Computer's primary workspace. Although true of most memory chips (ROMs, PROMs, etc.), "random" means that the contents of each byte can be directly accessed without regard to the bytes before or after it. RAM chips require power to maintain their content. See dynamic RAM, static RAM and memory.
• Raster Graphics for Imaging and Painting

Raster graphics is the TV-like method that uses dots to display an image on screen. Raster graphics images are created by scanners and cameras and are also generated by paint packages. A picture frame is divided into hundreds of horizontal rows, with each row containing hundreds of dots, called pixels.
Raster graphics images may take up more space on disk than their vector graphics counterpart, because storage for each pixel is required even if it's part of the background. A small object in vector graphics format will take up only a few vectors in the display list file. . Unlike TV, which uses one standard (NTSC) for the country, there are dozens of raster graphics standards. Also, unlike TV, which records and displays the dots as infinitely variable shades and colors (analog), computer graphics have a finite number of shades and colors (digital).
• raster graphics

In computer graphics, a technique for representing a picture image as a matrix of dots. It is the digital counterpart of the analog method used in TV. However, unlike TV, which uses one standard, there are many raster graphics standards. See graphics. Contrast with vector graphics
• Rendering

In computer graphics, creating a 3-D image that incorporates the simulation of lighting effects, such as shadows and reflection.
• resolution

Degree of sharpness of a displayed or printed character or image. On screen, resolution is expressed as a matrix of dots. A 680x400 resolution means 680 dots across each of 400 lines. The same resolution looks sharper on a small screen than a large one. For printers, resolution is expressed as the number of dots per linear inch. A 300dpi resolution means 90,000 dots per square inch (300x300).
• RGB

(Red Green Blue) Method of recording and generating colors in a video system. On a TV or color monitor, colors are displayed as varying intensities of red, green and blue dots. When red, green and blue are all turned on high, white is produced. As the intensities are equally lowered, shades of gray are produced. When all dots are turned off, the base color of the screen appears.
Color printing uses the CMY, or CMYK (Cyan Magenta Yellow blacK) system for mixing colors. In RGB, colors are added to create white. In CMY, colors are subtracted to create white. See colors.
• ROM

(Read Only Memory) Memory chip that permanently stores instructions and data. Its contents are created at the time of manufacture and cannot be altered. Used extensively to store control routines in personal computers (ROM BIOS) and in peripheral controllers, it is also used in plug-in cartridges for printers, video games and other systems. When software is stored in ROM, upgrading to the next version requires replacing the ROM chip. See PROM.
• rubber banding

In computer graphics, the moving of a line or object where one end stays fixed in position.
• scan line

One of many horizontal lines in a graphics frame.
• Scan

(1) In optical technologies, to view a printed form a line at a time in order to convert images into bitmapped representations, or to convert characters into ASCII text or some other data code.
(2) In video, to move across a picture frame a line at a time, either to detect the image in an analog or digital camera, or to refresh a CRT display.
(3) To sequentially search a file.
• SCSI

(Small Computer System Interface) Pronounced "scuzzy." SCSI is a hardware interface that allows for the connection of up to seven or 15 peripheral devices (hard disk, CD-ROM, scanner, etc.) to a single expansion board in the computer. The expansion board is called a SCSI host adapter or SCSI controller. SCSI is widely used as a hardware interface in all types and sizes of computers from micro to mainframe. In personal computers, SCSI has been directly supported by the Macintosh operating system, which has made the Mac a plug and play computer for years. Although Windows 95 supports SCSI, DOS and Windows 3.x do not. Attaching SCSI devices to a DOS or Windows 3.x system requires adding the appropriate SCSI driver.
• serial port

A socket on a computer used to connect a modem, mouse, scanner or other serial interface device to the computer. The Macintosh uses the serial port to attach a printer, whereas the PC uses the parallel port. Transferring files between two personal computers can be accomplished by cabling the serial ports of both machines together and using a file transfer program. The serial port uses DB-9 and DB-25 connectors. On the back of most newer PCs is one 9-pin male connector for serial port #1, named COM1 and typically used for the mouse, as well as one 25-pin male connector for serial port #2, named COM2 and typically used for a modem. In a PC, serial port circuits are contained on a small expansion card that plugs into an expansion slot. Typically two serial ports, one parallel port and one game port are on the card. These ports are often also included on an IDE host adapter card, which takes up only one expansion slot and provides hard and floppy disk control as well as I/O. Contrast with parallel port. See serial interface and RS-232. Why Serial and Parallel Ports? The serial port is designed primarily to accomodate modems, which require a serial connection to the telephone system. Data bits are passed one after the other (serially) over the single line provided by the telephone wiring. On the other hand, local devices such as a printer are not restricted to single-channel transmission. The parallel port, which contains eight lines for transmitting an entire byte (eight bits) simultaneously, provides a higher-speed pathway between the computer and a peripheral device. All other interfaces used in a computer, such as SCSI and IDE as well as the ISA, EISA and Micro Channel buses, are also parallel in design. They provide 8, 16 or 32 wires for simultaneous transfer of data bits.
• SGI

(Silicon Graphics, Inc., Mountain View, CA) A manufacturer of very high-end graphics workstations, founded in 1982 by Jim Clark. Its UNIX-based operating system is IRIX. SGI had been using MIPS processors for a number of years and acquired MIPS Computer Systems in 1992. Its current line is based on the MIPS R4000 64-bit CPUs (see MIPS Computer). No matter how much better the graphics get on personal computers, the graphics are always superior on SGI workstations. Running a flight simulator on an SGI machine is considerably more realistic than on a PC; however, SGI workstations can cost from 20 to 50 times as much. They are naturally used in commercial graphics applications, where the state of the art is always being pushed.
• SIGGRAPH.

A special interest group on computer graphics that is part of the ACM.
• soft copy

Refers to data displayed on a video screen. Contrast with hard copy.
• software

Instructions for the computer. A series of instructions that performs a particular task is called a program or software program. The two major categories are system software and application software.
System software is made up of control programs, including the operating system, communications software and database manager.
Application software is any program that processes data for the user (inventory, payroll, spreadsheet, word processor, etc.).
• solid modeling.

A mathematical technique for representing solid objects. It is the least abstract form of CAD. Unlike wireframe and surface modeling, solid modeling systems ensure that all surfaces meet properly and that the object is geometrically correct. A solid model can also be sectioned (cut open) to reveal its internal features. Solids allow interference checking, which tests to see if two or more objects occupy the same space.
• spline.

In computer graphics, a smooth curve that runs through a series of given points. The term is often used to refer to any curve. See Bezier and B-spline.
• Sun

(Sun Microsystems, Inc., Mountain View, CA) A manufacturer of network-based, high-performance workstations founded in 1982. Product lines include stand-alone and networked systems, diskless workstations and file servers that feature its SPARC microprocessor architecture. Sun supports an open systems model of computing throughout its product line that allows it to interact in networks of computer systems from other vendors. Its ONC (Open Network Computing) software is supported by over 300 vendors, and its NFS (Network File System) software, which allows data sharing across the network, has become an industry standard. In 1991, Sun split its business into the following wholly-owned subsidiaries: Sun Microsystems - Systems SunSoft - System software SunPro - Programmer productivity tools SunPics - Printing and imaging SunConnect - Network integration SunExpress - Distribution
• surface modeling

In CAD, a mathematical technique for representing solid-appearing objects. Surface modeling is a more complex method for representing objects than wireframe modeling, but not as sophisticated as solid modeling. Although surface and solid models can appear the same on screen, they are quite different. Surface models cannot be sliced open as can solid models. In addition, in surface modeling, the object can be geometrically incorrect; whereas, in solid modeling, it must be correct.
• surface normal

In 3-D graphics, an imaginary line that is perpendicular to the surface of a polygon. It may be computed at the vertex of a triangle, in which case it is the average of all the vertices of adjoining triangles. Or, it may be computed for each pixel in the triangle as in Phong shading. Surface normals are used to derive the reflectivity of a light source shining onto an object. See tessellation, triangle, Phong shading and Gouraud shading.
• surfing

Scanning online material, such as databases, news clips and forums. The term originated from "channel surfing," the rapid changing of TV channels to find something of interest.
• surge protector.

A device that protects a computer from excessive voltage (spikes and power surges) in the power line. See voltage regulator and UPS.
• Targa

A raster graphics file format developed by Truevision, Inc., Indianapolis, IN. It uses the .TGA file extension and handles 16-, 24- and 32-bit color. It is also the trade name of a line of video graphics boards used in high-resolution imaging.
• thermal wax transfer

A printing process that transfers a waxlike ink onto paper. For example, in a color printer, a mylar ribbon is used that contains several hundred repeating sets of full pages of black, cyan, magenta and yellow ink. A sheet of paper is pressed against each color and passed by a line of heating elements that transfers the dots, or pixels, of ink onto the paper.
• TIFF

(Tagged Image File Format) A widely-used raster graphics file format developed by Aldus and Microsoft that handles monochrome, gray scale, 8-and 24-bit color. TIFF allows for customization, and several versions have been created, which does not guarantee compatibility between all programs. TIFF files are compressed using several compression methods. LZW provides ratios of about 1.5:1 to 2:1. Ratios of 10:1 to 20:1 are possible for documents with lots of white space using ITU Group III & IV compression methods (fax). See JPEG.
• true color

(1) The ability to generate 16,777,216 colors (24-bit color). See high color. (2) The ability to generate photo-realistic color images (requires 24-bit color minimum).
• Vector Graphics and Raster Graphics

Two methods are used for storing and maintaining pictures in a computer. The first method, called vector graphics (also known as object-oriented graphics), maintains the image as a series of points, lines, arcs and other geometric shapes.
The second method, called raster graphics, resembles television, where the picture image is made up of dots. Understanding these two methods and how they intertwine in today's graphics systems is essential for mastering computer graphics. When you create an image on the computer, you may not know which method is used, but when you try to manipulate that image, it will become obvious.
Vector graphics can be transmitted directly to x-y plotters that "draw" the images from the list of vectors. Older CAD systems used vector screens that also drew the vectors. Today, all monitors are raster graphics displays made up of dots, and the vectors are "rasterized" into the required dot patterns by hardware or software.
Vector Graphics for CAD and Drawing Vector graphics is the method employed by computer-aided design (CAD) and drawing packages. As you draw, each line of the image is stored as a vector, which is two end points on an x-y matrix. For example, a square becomes four vectors, one for each side. A circle is turned into dozens or hundreds of tiny straight lines, the number of which is determined by the resolution of the drawing. The entire image is commonly stored in the computer as a list of vectors, called a display list.
• vector

(1) In computer graphics, a line designated by its end points (x-y or x-y-z coordinates). When a circle is drawn, it is made up of many small vectors.
• virtual reality

An artificial reality that projects the user into a 3-D space generated by the computer. It requires the use of a unique kind of glove, called a data glove, and stereoscopic goggles, which are both wired to the computer. The glove lets users point to and manipulate computer-generated objects that are displayed on tiny monitors inside the goggles. Virtual reality, or VR, can be used to create any illusion of reality or imagined reality and is used both for entertainment and training. Virtual reality has been around for some time now. For example, flight simulators, used to train airplane pilots and astronauts, have provided a very realistic simulation of the environment, albeit extremely expensive. A relatively new variation of virtual reality, known as unencumbered virtual reality or computer automatic virtual environment (CAVE), is becoming popular for entertainment. For example, using a glove, but not goggles, you can play a simulated ballgame such as volley ball or basketball. A video camera captures your movements while you watch yourself on a large screen. You hit a simulated ball that is passed to you by your on-screen opponent and play the game as if it were real. See HMD, CAVE, 6DOF and cyberspace.
• warm boot

Restarting the computer by performing a reset operation (pressing reset, Ctrl-Alt-Del, etc.). See cold boot and boot.
• WAV

A Windows sound file, which uses the .WAV extension. Wave files take up a lot of disk space. Depending on sampling frequency and rate, one minute of audio, without compression, can take from 644KB to 5MB. See sound card.
• whiteboard

The electronic equivalent of chalk and blackboard. Whiteboards allow participants across a network to simultaneously view one or more users drawing on the computer.
• wireframe modeling

In CAD, a technique for representing 3-D objects, in which all surfaces are visibly outlined in lines, including the opposite sides and all internal components that are normally hidden from view. Compared to surface and solid modeling, wireframe modeling is the least complex method for representing 3-D images.
• workstation

(1) High-performance, single user microcomputer or minicomputer that has been specialized for graphics, CAD, CAE or scientific applications.
(2) In a LAN, a personal computer that serves a single user in contrast with a file server that serves all users in the network.
(3) Any terminal or personal computer.
• WYSIWYG

(What You See Is What You Get) Pronounced "wizzy-wig." Refers to text and graphics appearing on screen the same as they print. To have WYSIWYG text, a screen font must be installed that matches each printer font. Otherwise, a 24-point font may display in correct size relationship to a 10-point font, but it won't look like the printed typeface. It is almost impossible to get 100% identical representation, because screen and printer resolutions rarely match. Even a 300 dpi printer has a higher resolution than almost every monitor.