ARC603  Drawing II, Digital


left-arrow.gif (166 bytes)Return to course home page.

blackdot.gif (49 bytes)
Links to other dictionaries or encyclopedias of computer related terms
The PC Webopedia
Hey, I didn't make up this name!
An interactive dictionary of computing terms. Lengthier but more complete definitions.
blackdot.gif (799 bytes)
Course Glossary
This glossary is not encyclopedic. It is not intended to be. Terms used within a specific application program are usually defined by a glossary or users manual or reference guide for the software itself. This highly selective list represents terms used within the course plus those with which a person of similar experience should be familiar.
blackdot.gif (799 bytes)
Some terms with similar meanings Some common symbolic conventions Kilo, mega, giga, tera, peta, and all that
blackdot.gif (799 bytes)
access time
The time it takes to locate and retrieve data from memory, typically secondary memory.
The ability to read, write or execute files or directories. Access privileges are established by the owner of a file or directory and determine what other users may do with a directory or its contents.
active window
The current window. The window through which one communicates with the programs or processes that are running. Typically one process can be assigned to one window and a time. .
A name or number which points to a location of data in primary or secondary memory.
In   image generation, aliasing is the generation of a false (alias) frequency along with the correct one when doing frequency sampling. For images, this produces a jagged edge, or stair-step effect. See Antialiasing.
Relating to numbers, letters, and punctuation marks.
A specific set of instructions design to solve a specific problem, such as an algorithm to find a maximum value or to sort data in a particular way.
The term algorithm (pronounced AL-go-rith-um) is a procedure or formula for solving a problem. The word derives from the name of the mathematician, Mohammed ibn-Musa Al-Khowarizmi, who was part of the royal court in Baghdad and who lived from about 780 to 850. Al-Khowarizmi's work is the likely source for the word algebra as well.
A computer program can be viewed as an elaborate algorithm. In mathematics and computer science, an algorithm usually means a small procedure that solves a recurrent problem.
Antialiasing is the smoothing of the image roughness caused by aliasing. Methods include adjusting pixel positions or setting pixel intensities so that there is a more gradual transition between the color of a line and the background color.
application program
A program (software) that performs substantive tasks, such as a word processing program, a database program, a spreadsheet program or a CAD program. As distinct from operating system software or utility programs. array
A list or table of values which can be addressed as a single variable.
AI Artificial Intelligence.
The ability of a machine to learn, to reason, to mimic human capabilities.
American Standard Code for Information Interchange. The most often used coding system for characters (text).
ASCII file
A file whose contents is text, represented in ASCII form. A file without formatting instructions. Used to transfer text from one application program, usually a word processing program, to another.
An intermediate level CAD software package, for generic drafting. The most often used CAD software. There are many third party software packages which can be used together with AutoCAD to make it discipline specific.
assembly language
A low-level language which is close to machine language.
The transmission of data at irregular intervals. As opposed to synchronous.
1. A element of data in a database . 2. In some programs, a descriptive or organizational characteristic that can be assigned to a graphic element.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
back-up copy
A copy preserved, usually on a different medium, as protection from loss or destruction of original data.
An easy to learn programming language.
batch file
A command file or script file. A file which contains a list of instructions to be carried out without interaction with the user.
batch processing
Execution of a batch file or files, without interaction with a user. The grouping of processes (into a batch) for execution at one time.
Commonly understood as "bits per second". A measure of the rate at which electronic impulses can be transmitted over a phone line.
beta test
Hardware and software testing in a work environment. The final stage of testing prior to public release.
Bezier curve (bez ee-ay)
A type of curves calculated mathematically that connects two points to form a smooth, free-form curve or surface. Bezier curves require few points to define a large number of shapes - thus the advantage over methods of defining curves, such as bits or mathematical expressions.
Bezier.curve.gif (6132 bytes)
Referring to the base 2 system of mathematics.
Binary digit.
The smallest unit of information that a computer can process or store. Based on binary mathematics, the value of a bit may be either 0 or 1 (zero or one) and may represent the numbers 0 and 1, or true and false, or on and off, or black and white.
bit map, often written bitmap
An ordered set of bits that control the pixels on the display. Each bit controls one pixel. The contents of the bit map are determined by the software. The bit map is stored in the screen buffer, or video memory (VRAM).

A bit map does not need to contain a bit of color-coded information for each pixel on every row. It only needs to contain information indicating a new color as the display scans along a row. Thus, an image with much solid color will tend to require a small bit map.

Because a bit map uses a fixed or raster graphics method of specifying an image, the image cannot be immediately rescaled by a user without losing definition. A vector graphics graphic image, however, is designed to be quickly rescaled. Typically, an image is created using vector graphics and then, when the artist is satisifed with the image, it is converted to (or saved as) a raster graphic file or bit map.

bit depth
The number of colors available on a system is determined by the bit depth, which is the number of bits of information
used to represent a single pixel on the monitor. The lowest number of bits used for modern desktop color monitors is
usually 8 bits (256 colors); 16 bits provide for thousands of colors (65,536, to be exact); and 24 bits, common on
newer systems, provide for millions of colors (16,777,216). The specific colors available on a system are determined
by the way in which the target platform allocates colors. Available colors might differ from application to application.
(from Sun's web site)
A group of data (bits or bytes) read in or written out in a single transaction. Many operating systems prefer to manage blocks rather than single bytes. Blocks can be 512 or 1024 bytes.
Pertaining to the algebra developed by the French matematecian George Boole (1815-64).
Boolean algebra
Algebra similar in form to ordinary algebra, but with   classes and propositions for variables rather than data values. It includes the operators AND, OR (inclusive or), XOR (exclusive or), NOT, EXCEPT, IF, and THEN.
Boolean variable
Use of two valued Boolean algebra to either one of two values possible. Examples would be true or false; on or off; open or closed.
Boolean operations
An operation in Boolean algebra performed on or with two operands and in which the result is dependent upon both of them. Such operands are typically represented with connective symbols
Examples in CAD would be:
AND (element A AND element B), also called a "union" in which two graphic elements may be joined (unioned) to produce a new, third, object.
NOT (element A BUT NOT B), also called a "subtraction" in which one graphic element is subtracted from another to produce a new, third, element.
OR (element A OR B), also called a "split" in which two intersecting graphic elements are split into three new graphic elements.
boot (or reboot)
Starting (or restarting) the computer system. The computer performs an internal check of its systems, verifies the various peripheral devices that may be attached and starts the operating system running.
An area of memory that is used to temporarily store information. Many application programs establish buffers for data that has been deleted, allowing the user to retrieve or transfer the data. Many printers and plotters have memory, called a print buffer, that temporarily holds data sent from the computer while it waits to be printed relieving the computer and its RAM.
An error in a program or a computer system.
The communication pathway within the computer system that transmits data from one part of the system to another. The 'width' of the bus is measured in bits, thus a 16 bit bus can transmit 16 bits simultaneously. The speed of the bus is controlled by the system's clock, measured in Hz.
An icon, or image, displayed on the monitor which resembles a pushbutton. May be used to select (with the cursor) various actions.
A unit if information, typically eight bits. Can be used to represent one character or one number or one component of an image. Files are often measured in bytes, kilobytes, megabytes, gigabytes and terabytes.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
High speed RAM, closely associated with the CPU. Memory cache holds data waiting to be processed by the CPU. Disk cache holds data waiting to be read to disk. It also stores information often called from disk, such as a listing of files. Use of caching speeds the transfer of data.
Computer Aided Design. Sometimes used as Computer Assisted Design. Sometimes used as Computer Aided Drafting.
Computer Aided Design and Drafting.
Computer Assisted Instruction.
Computer Aided Manufacture.
In spreadsheet software, the intersection of one row and one column. Used as an address for data.
Central Processing Unit. or CPU
See CPU.
One unit of alphanumeric data.
close (a file)
To close a file is to save a file, to copy the contents of the file from primary memory (RAM) to secondary memory (usually disk). The process insert a marker in the File Allocation Table (FAT) on the disk indicating that there is no more to the file.
In personal computer storage technology, a cluster is the logical unit of file storage on a hard disk; it's managed by the computer's operating system. Any file stored on a hard disk takes up one or more clusters of storage. A file's clusters can be scattered among different locations on the hard disk. The clusters associated with a file are kept track of in the hard disk's file allocation table (FAT). When you read a file, the entire file is obtained for you and you aren't aware of the clusters it is stored in.
Since a cluster is a logical rather than a physical unit (it's not built into the hard disk itself), the size of a cluster can be varied. The maximum number of clusters on a hard disk depends on the size of a FAT table entry. Beginning with DOS 4.0, the FAT entries were 16 bits in length, allowing for a maximum of 65,536 clusters. Beginning with the Windows 95 OSR2 service release, a 32-bit FAT entry is supported, allowing an entry to address enough clusters to support up to two terabytes of data (assuming the hard disk is that large!).
The tradeoff in cluster size is that even the smallest file (and even a directory itself) takes up the entire cluster. Thus, a 10-byte file will take up 2,048 bytes if that's the cluster size. In fact, many operating systems set the cluster size default at 4,096 or 8,192 bytes. Until the file allocation table support in Windows 95 OSR2, the largest size hard disk that could be supported in a single partition was 512 megabytes. Larger hard disks could be divided into up to four partitions, each with a FAT capable of supporting 512 megabytes of clusters.
COmmon Business Oriented Language, A high level programming language used for business applications.
color wheel
A method of designating aspects of color, in particular hue. Measured as if degrees on a 360 degree circle.
color cube
A method of representing colors, both additive and subtractive, on a cube.
color.cube.gif (7251 bytes)
color, bits
see bit depth
An instruction to a computer that triggers a process, which may be one or more instructions.
The translation of a high (human) level programming language program into a low (machine) level language program.
The component of the computer system (hardware) that is the primary communication device between the user and the system.
A microprocessor or auxiliary processor optimized for a specific type of operation, such as floating point mathematics, video processing or 3D data processing. Relieves load on the CPU.
1. The relationship of the various physical parts of a computer system. 2. The settings of the software which control the communication of the hardware components for a computer system.
core memory
Primary memory (RAM). Originally primary memory was magnetic and the direction of the magnetic field (clockwise or counterclockwise) was used to represent zero or one.
core dump
The writing out (dumping) of the entire contents of primary memory. In some systems in it written to a file named core . When analyzed by specialized software it may indicate the nature of the problem. Usually indicates a serious problem.
Central Processing Unit. The hardware portion of a computer system that does the actual computation. The power of the CPU is measured by the number of bits it can process at one time (a 32 bit CPU can process 32 bits with each tick of the clock) and the speed with which it can process the data which is controlled by the system clock (stated in kilohertz, megahertz or gigahertz). The more bits a CPU can process and the faster it can process them, the more powerful it is.
Cathode Ray Tube, the actual part of a display or monitor that projects cathode rays onto the interior surface of the screen. Informal term for the display or monitor. Erroneous term for an entire computer system.
A pointer on the display or monitor. Controlled by various techniques, such as the control arrows on a keyboard, a mouse, a stylus or a puck.
current default
A value, typically set by the user. Once set it  is applied without the user's continuing interaction. As opposed to default.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
Representation of information, facts. data can be numbers, characters or other types, such as graphic.
1. A computer program (software) used to manipulate information (data).
2. A form or format that is prepared to store and manipulate data.
3. The content, the data, the information stored or being manipulated. The terms are often used interchangeably.
database is a collection of data that is organized so that its contents can easily be accessed, managed, and updated. The most prevalent type of database is the relational database, a tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways. A distributed database is one that can be dispersed or replicated among different points in a network.
Process of locating and correcting errors in software.
A value or setting that a computer system assumes. Such values are typically set by the hardware or software designers. Some programs allow such values to be changed by the user. See current default.
degenerate polygon. Also known as a warped polygon
A polygon defined by four or more nodes (points) which are not coplanar. Many CAD databases will permit such a polygon to be defined but they will cause problems in rendering (casting shadows) and when executing Boolean operations which require the calculation of intersections.
Process of converting data from analog form to digital form.
digitizing tablet
A data input device. A surface (tablet) together with a pointing device (a mouse, puck or stylus) that is used to draw or trace images which converts the information into digital form.
A special type of file, able to contain files or names of files or other directories. Used as an organization strategy.
Display device, screen, monitor. A device for displaying text and graphic images.
display list
A sorted list of graphic elements to be sent to the screen, typically sorted beginning with the element farthest from the eye point  and concluding with the element closest to the eye point. When sent to the screen and displayed in this order, the resultant image can appear to have the properties of a three dimensional object.
One form of secondary memory. data storage media. A 3 1/2" or 5 1/4" plastic disk capable of storing data in magnetic form. Also called floppy disk.
disk drive
One form of secondary memory. A data storage device. data can be read to and written from a disk drive. Access times are slower than RAM but much faster than diskette. The cost per bit of data is less than RAM and less that diskette. data is stored in magnetic form which is non-volatile (not effected by a power supply).
Disk Operating System. The housekeeper. A program (software) which controls many of the computers functions, including the management of files on disk or diskette.
Dynamic Random Access Memory. Another name for RAM. Dynamic refers to its volatility, the loss of it contents when electricity is turned off.
A program (software) that controls (drives) a peripheral device, such as a plotter or printer. Must be specific to the peripheral device.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
Encapsulated PostScript
(EPS) An extension of the PostScript graphics file format developed by Adobe Systems. EPS is used for PostScript graphics files that are to be incorporated into other documents. An EPS file includes pragmas (special PostScript comments) giving information such as the bounding box, page number and fonts used.
On some computers, EPS files include a low resolution version of the PostScript image. On the Macintosh this is in PICT format, while on the IBM PC it is in TIFF or Microsoft Windows metafile format.
E-mail or email
Electronic mail. An application which replicates components of a mail system. Allows users to prepare messages, send messages or files, receive messages or files.
Erasable Programmable Read Only Memory. Permanent memory within the computer that can be erased and programmed with special equipment.
A commonly used high-speed network.
expansion card
A component of hardware, a circuit board that can be added (inserted) into the computer system to provide additional capabilities, such as increased memory, networking, printer control or display control. Allows a computer system's configuration to be modified.
expert system
A knowledge-based system within artificial intelligence. One which seeks to mimic the knowledge of an expert in an interactive setting.
An addition to a file's name, used to indicated the type of file, such as text, graphic, or program. Usually assigned by an application program.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
facilities management
An application program which allows users to describe, store, and manipulate information relating to buildings, such as room occupancies or use, furniture, maintenance of systems, etc. facsimile Ability to electronically transmit and receive copies of documents. FAX for short.
File Allocation Table. A table that is established at the beginning of each disk (hard or otherwise) during formatting. The FAT maintains the information regarding filenames and the physical address on the disk of all of the data
A file allocation table (FAT) is a table that an operating system maintains on a hard disk that provides a map of the clusters (the basic units of logical storage on a hard disk) that a file has been stored in. When you write a new file to a hard disk, the file is stored in one or more clusters that are not necessarily next to each other; they may be rather widely scattered over the disk. A typical cluster size is 2,048 bytes, 4,096 bytes, or 8,192 bytes. The operating system creates a FAT entry for the new file that records where each cluster is located and their sequential order. When you read a file, the operating system reassembles the file from clusters and places it as an entire file where you want to read it. For example, if this is a long Web page, it may very well be stored on more than one cluster on your hard disk.
Until Windows 95 OSR2 (OEM Release 2), DOS and Windows file allocation table entries were 16 bits in length, limiting hard disk size to 128 megabytes, assuming a 2,048 size cluster. Up to 512 megabyte support is possible assuming a cluster size of 8,192 but at the cost of using clusters inefficiently. DOS 5.0 and later versions provide for support of hard disks up to two gigabytes with the 16-bit FAT entry limit by supporting separate FATs for up to four partitions.
With 32-bit FAT entry (FAT32) support in Windows 95 OSR2, the largest size hard disk that can be supported is two terabytes.
A data element in a database.
A named, ordered set of data, stored in secondary memory, with a unique address (name). Files may contain data (text, numbers, binary data representing graphic information) or programs (sets of instructions to be executed) connected to the file name. The actual content of the file may be distributed throughout a disk, but its physical location (address) is maintained in the File Allocation Table.
File Transfer Protocol
File Transfer Protocol (FTP), a standard Internet protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet's TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to download programs and other files to your computer from other servers.
As a user, you can use FTP with a simple command line interface (for example, from the Windows MS-DOS Prompt window) or with a commercial program that offers a graphical user interface. Your Web browser can also make FTP requests to download programs you select from a Web page. Using FTP, you can also update (delete, rename, move, and copy) files at a server. You need to logon to an FTP server. However, publicly available files are easily accessed using anonymous FTP.
Basic FTP support is usually provided as part of a suite of programs that come with TCP/IP. However, any FTP client program with a graphical user interface usually must be downloaded from the company that makes it.
fixed disk
Another term for hard disk.
flat file
A database structure with a single table. The simplest form of database.
FLOating Point operations per Second. The speed with which a CPU can perform mathematical operations that involve real numbers. A measure of the speed of a CPU.
The arrangement (form) of something, typically the data in a file. ASCII, DXF, TIFF, IGES are examples of file formats.
format (disk)
A process which prepares a disk or diskette to accept data. The operating system controls the formatting process. Different disks and different computer systems require different formats. Produces a blank but usable disk.
FORmula TRANslator. A high level programming language used for scientific applications.
1. In film and video recording and playback, a frame is a single image in a sequence of images that are recorded and played back. 2. In computer video display technology, a frame is the image that is sent to the display image rendering devices. It is continuously updated or refreshed from a frame buffer, a highly accessible part of video RAM.
frame buffer
Another term for VRAM, Video Random Access Memory. Stores the bit which controls the display. Same as screen buffer.
See File Transfer Protocol.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
Approximately one billion bytes (2 to the 30 = 1,073,741,824).
A graphics file format. Includes gif89a. Often pronounced with a hard g although the original and (for some at least) preferred pronunciation is JIF. Stands for Graphics Interchange Format which, together with GIF, are service marks of CompuServe Incorporated. GIF is a file compression algorithm which is intended to be a "non-lossy" process, meaning no loss of image data. It is ideal for black and white images, in particular line drawings. Images with tonal range, such as photographs, are better compressed in jpeg format. The compression is to allow faster transmission of image files across the internet. Thus a gif file format is used when the image to be placed on a web page.
On the Web and elsewhere on the Internet the GIF has become a de facto standard form of image. The LZW compression algorithm used in the GIF format is owned by Unisys.
The GIF uses the 2D raster data type and is encoded in binary. There are two versions of the format, 87a and GIF89a. Version 89a (July, 1989) allows for the possibility of an animated GIF, which is a short sequence of images within a single GIF file. A GIF89a can also be specified for interlaced GIF presentation.
A patent-free replacement for the GIF, the Portable Network Graphics (PNG) format, has been developed by an Internet committee and major browsers support it or soon will.
Garbage In, Garbage Out.
graphic element
a. data that can be displayed as a graphic image (as opposed to characters or numbers).
b. data that can be treated as a single entity.
c. Whatever a CAD program declares to be a graphic element.
In UNIX operating systems, user access privileges may be set for the owner of the file, members of a group and all users of the system. All users are members of a group. The specific group is determined by the system administrator.
Graphical User Interface. A program (software) that permits display and control of computer functions by graphic means, as opposed to control by commands typed at a keyboard.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
hard drive
A data storage device, used for mass memory, the storage of large quantities of data. It is made of spun aluminum and is permanently sealed in a housing. Faster and cheaper (per unit of data) than diskette, slower and cheaper than RAM. Non volatile and non portable. data is stored in magnetic form which is permanent.
hard disk
Another term for hard disk.
The physical, tangible portion of a computer system, including the CPU, display devices, storage devices, output devices, etc. As opposed to software.
One cycle per second. Used to measure CPU speed and monitor refresh rates.
host, host computer
The processor which controls an entire computer system.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
IC, IC board
see integrated circuit.
A pictorial or graphic representation of something, usually a file, a window, or a button.
To prepare or to begin. Some programs, such as X windows, are started by an initialization command.
data submitted to the computer from an input device for processing or storing. See also Output.
integrated circuit
An electronic circuit that is contained within a single piece of semiconductor material, typically silicon.
intelligent terminal
A terminal with computing capabilities, with a CPU.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
jpeg, jpg
Stands for Joint Photographic Experts Group (pronounced JAY-peg). The original name of the committee that designed a standard image compression algorithm. JPEG is designed for compressing either full-color or gray-scale digital images that have a range of tonal or color values. It is not ideal for line drawings. JPEG does not handle compression of black-and-white (1 bit-per-pixel) images or moving pictures. The amount of compression can be determined by the maker of the image. The process is called a "lossy" process because some of the detail is removed in the compression process. jpeg files are typically intended for use on web pages since the smaller file size that results speeds transmission of the image across the internet. The software that displays the image (the browser) must be able to uncompress the data. The greater the degree of compression, the greater the loss of data. The most common standard for compressing movies are known as MPEG.
Together with the Graphic Interchange Format (GIF) and Portable Network Graphics (PNG) file formats, the JPEG is one of the image file formats supported on the World Wide Web, usually with the file suffix of ".jpg". You can create a progressive JPEG that is similar to an interlaced GIF.


left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
An input device with keys which allows typing data for input.
In animation, a critical (key) point of view (frame) set by the user. The software interpolates the intervening views (frames) prior to rendering each frame.
kilobyte (KB or kb)
Approximately 1,000 bytes (2 to the 10 = 1024 bytes). See also byte, megabyte, gigabyte, terabyte.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
A highly ordered set of instruction which possess aspects of human language, particularly syntax (grammar) and vocabulary.
Local Area Network. A system which interconnects device in a limited area, a room.
LISt Processing. A high level programming language. Used in artificial intelligence.
To open a file, to copy the data from disk to RAM. Note that it is a copying process.
loft curve
A curve which passes through its control points, as opposed to a Bezier curve.
logical operator
Allows information to manipulated using principles of formal logic, in particular the AND, inclusive OR, exclusive OR, NOT comparisons.
A set of instructions in a program that are repeated.
lossless and lossy compression
Lossless and lossy compression are terms that describe whether or not, in the compression of a file, all original data can be recovered when the file is uncompressed. With lossless compression, every single bit of data that was originally in the file remains after the file is uncompressed. All of the information is completely restored. This is generally the technique of choice for text or spreadsheet files, where losing words or financial data could pose a problem. The Graphics Interchange File (GIF) is an image format used on the Web that provides lossless compression.
On the other hand, lossy compression reduces a file by permanently eliminating certain information, especially redundant information. When the file is uncompressed, only a part of the original information is still there (although the user may not notice it). Lossy compression is generally used for video and sound, where a certain amount of information loss will not be detected by most users. The JPEG image file, commonly used for photographs and other complex still images on the Web, is an image that has lossy compression. Using JPEG compression, the creator can decide how much loss to introduce and make a trade-off between file size and image quality.
low-level language
A computer programming language that is specific of a particular CPU. As opposed to a high (human) level language.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
main memory
Another term for RAM, or random access memory. Often called system memory or working memory.
megabyte (MB or mb)
Approximately 1 million bytes (2 to the 20 = 1,048,576 ). See also kilobyte, gigabyte.
The hardware portion of a computer system that stores information. See also main memory, system memory, working memory, and RAM.
A list of options displayed on the screen from which the user may select. The cursor may be moved over the menu items (usually with a mouse) for selection.
Megahertz. One million hertz.
A 3 1/2" plastic disk for data storage. Made of rigid plastic in a rigid plastic sleeve.
A CPU on a single silicon chip. As opposed to a multi chip CPU.
A 5 1/4" plastic disk for data storage. Made of somewhat flexible (thus floppy) plastic in a soft plastic sleeve.
Million Instructions Per Second. The speed with which a CPU can procession instructions. A measure of the power of a CPU.
The process of mirroring or reflecting a graphic element about an axis of symmetry. The mathematical process is one of multiplication by minus one, a process of negation.
MOdulate-DEModulate, or MOdulator-DEModulator. An input and output device which permits computers to communicate over ordinary telephone lines. Converts internal computer system communications, which are typically parallel, to serial form.
modem port
A connector or socket. If the modem is internal (within the system box) it is the connector to which the telephone is connected. If the modem is external (outside the system box) it is the connector to which the modem is connected.
A high-level computer programming language. Noted for its self contained subdivisions which can be combined to form a new program.
An output device for display of test or graphic information. Uses cathode ray (raster) technology, similar to a television screen. Also called display, CRT or screen.
Computer circuit board that contains the CPU, memory chips, I/O controlling chips and main communication bus.
An input device. A hand held device that is moved across a table surface which controls the movement of the cursor.
Microsoft - Disk Operating System. Same as DOS or PC-DOS The most common operating system for IBM PCs and compatibles. Developed by Microsoft Corporation .
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
One billionth of a second.
An interconnected system of computers and peripheral devices. The term often refers to the system of wires and related hardware and software which provide the interconnection itself. Permits communication and sharing of devices, data and computer resources.
Having to do with numbers, from 0 to 9. Compare to alpha.
Non-Uniform Rational B-Spline, a mathematical representation of a 3-dimensional object. Most CAD applications support NURBS, which can be used to represent analytic shapes, such as cones, as well as free-form shapes.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
data that is accessible or hardware that is controlled.
To open a file is to load a file, to copy the contents of the file from disk to RAM. Renders the contents of a file accessible.
operating System
The program (software) that controls the internal workings of the computer system together with its peripheral devices. Performs basic housekeeping tasks, including interference checking (traffic control), passing data to and from devices and managing data in memory.
data that is produced by processes. The result of processing data. data transferred from the CPU to another external device, such as the monitor, disk, printer, etc. As opposed to input.
The name of the user with access privileges to certain files and directories. The owner of a file or directory may establish the access privileges for the group and for all others on the system.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
1.A portion of a program that is loaded into main memory when needed; a process called paging or swapping.
2. One screen of information, or one window of information (similar to one page of a document).
page space
An amount of hard disk reserved for swapping or paging portions of a program, used as an extension of RAM. Moving portions of a program from hard disk to RAM.
parallel computer
A computer with more than one CPU, thus able to process more than one instruction at a time. A coarse grained parallel computer has few but powerful CPUs (2 to 16) while a fine grained, or massively parallel, computer has many, but less powerful, processors (up to 64,000).
parallel port
A connector or socket on the computer, capable of passing electronic data in parallel fashion, for example, 16 bits at a time. As opposed to serial port which can only pass data one bit at a time.
parallel processing
In a parallel computer, the process of dividing a task into subtask and assigning them to various processors.
parametric model, parametric modelling
Any of a set of physical properties whose values determine the characteristics or behavior of something. In CAD, 2D and 3D objects can be stored in a database by its type together with a set of parameters. The parameters can later be edited without having to recreate the object.
The process of systematically analyzing and translating a command line prior to submission to the CPU.
In personal computers, a partition is a logical division of a hard disk created so that you can have different operating systems on the same hard disk or to create the appearance of having separate hard drives for file management, multiple users, or other purposes. A partition is created when you format the hard disk. Typically, a one-partition hard disk is labeled the "C:" drive ("A:" and "B:" are typically reserved for diskette drives). A two-partition hard drive would typically contain "C:" and "D:" drives. (CD-ROM drives typically are assigned the last letter in whatever sequence of letters have been used as a result of hard disk formatting, or typically with a two-partition, the "E:" drive.)
When you boot an operating system into your computer, a critical part of the process is to give control to the first sector on your hard disk. It includes a partition table that defines how many partitions the hard disk is formatted into, the size of each, and the address where each partition begins. This sector also contains a program that reads in the boot sector for the operating system and gives it control so that the rest of the operating system can be loaded into random access memory.
Boot viruses can put the wrong information in the partition sector so that your operating system can't be located. For this reason, you should have a back-up version of your partition sector on a diskette known as a bootable floppy.
A high level procedure oriented programming language.
A unique word or string of characters, initially established by the system administrator but changeable by the user. A means of validating that a prospective user has appropriate access and system usage privileges. A security mechanism.
The logical route the operating system must follow through directories and subdirectories to reach a specific file.
peripheral device
A component of hardware used together with and controlled by the computer. Typically input and output devices such as printers, monitors, modems, keyboards, etc.
PC Personal Computer.
Generically any personal computer. More specifically one develop by IBM Corporation or one which is compatible to it.
Personal Computer Disk Operating System. Same as DOS and MS-DOS. The operating system for IBM PCs and compatibles, developed by Microsoft Corporation and marketed by IBM Corporation.
Personal Computer
PC. A computer system which is single user and single tasking.
An operating system term, in both DOS and UNIX, which redirects the output of one process to become the input of another.
A PIcture ELement. The smallest dot that the computer's monitor can display. On a black and white monitor, one pixel is controlled by one bit. Therefore there is a correspondence between the location of a bit in the bit map and the location of a pixel on the screen.
Programming Language 1. A high level procedure oriented programming language.
1.) another term for the cursor; 2.) an i-node or link between two files constitutes a pointer from one file to another.
 The union of several line segments that are joined together so as to completely enclose an area.
A connector or socket on the computer where cables can be connected, used to connect peripherals. See also serial port and parallel port.
An output device, used to draw (plot) graphic images. Various technologies include pen, electrostatic, laser, thermal and ink jet.
primary storage, memory
RAM. Another term for main memory, memory. As opposed to secondary memory (hard disk or tape).
An output device, typically for smaller sheet sizes (8 1/2 x 11 or A size) with text. Many printers are also capable of printing graphic images. Various technologies include dot matrix, laser and ink jet.
printer port
The connector on the computer to which the printer is connected.
The ability to control access to files and directories. Privileges include the ability to read from, write to and execute a file.
In software, a transaction, an act which transforms data in some way. Requires input and produces output.
Typically, the Central Processing Unit (CPU). In fact, any component of the computer's hardware that calculates or computes. In personal computers, the processor is small, a microprocessor, and is made of an integrated circuit on a single chip. In workstations or larger systems, more than one processor may be used. A processor may also be dedicated to a specific function, such as controlling the display aspects (a video processor) or the plotter. Thus, modern computer systems have many processors.
A set of instructions. Controls various actions of the computers resources and manipulates data to perform useful tasks. Computer programs are also referred to, collectively, as software. A program may be written by a user or may be professionally written and purchased. Programs must comply with specific conventions governing their syntax and semantic content, thus forming programming languages.
program register
A type or memory which stores the address (a pointer to the location) of the next instruction to be processed.
A programming language used in artificial intelligence applications.
Programmable Read Only Memory. Read Only Memory which the user can load programs and data.
A message or symbol, generated by a program, which indicates that the program is ready to receive instruction, or which leads the user to respond in particular way.
Rules which control the way data are transmitted.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
Random Access Memory. data storage device. RAM is fast (data can be read to or written from RAM quicker than any other storage media) but is expensive (per unit of data). RAM is volatile (requires continuous flow of electricity, thus data is lost if electric power is cut off).
A group of cells or data, defined by a starting and ending number or identifier..

Also see frame, raster graphics, and raster image processor.
The term raster refers to the region of a cathode ray tube (CRT) or liquid crystal display (LCD) monitor that is capable of rendering images.
In a CRT, the raster is a sequence of horizontal lines that are scanned rapidly with an electron beam from left to right and top to bottom, in much the same way as a TV picture tube is scanned. However, there are certain differences. In general, the resolution is better in a computer CRT than in a TV picture tube. Also, a TV raster scan is interlaced, while the raster scan in a computer CRT is almost always non-interlaced. In a CRT, the raster is slightly smaller than the full screen size of the monitor. The height and width of the raster can be adjusted, as can the horizontal and vertical position.
In an LCD, the raster (usually called a grid) is scanned differently than in a CRT; image elements are displayed individually. The raster normally matches the screen monitor in size. But if low resolution is used (for example, 640x480 pixels on an LCD intended for 800x600), the displayed image may fill only part of the screen. If high resolution is used (such as 1024x768 pixels on an LCD intended for 800x600), the displayed image may exceed the area of the screen, and scrolling will be necessary to view all portions of the raster.

raster graphics
Raster graphics are digital images created or captured (for example, by scanner in a photo) as a set of samples of a given space. A raster is a grid of x and y coordinates on a display space. (And for three-dimensional images, a z coordinate.) A raster image file identifies which of these coordinates to illuminate in monochrome or color values. The raster file is sometimes referred to as a bit because it contains information that is directly mapped to the display grid.
A raster file is usually larger than a vector graphics image file. A raster file is usually difficult to modify without loss of information, although there are software tools that can convert a raster file into a vector file for refinement and changes. Examples of raster image file types are: BMP, TIFF, GIF, and JPEG files.
raster image processor
RIP is also an abbreviation for Routing Information Protocol.
A raster image processor (RIP) is a hardware or combination hardware/software product that converts images described in the form of vector graphics statements into raster graphics images or bits. For example, laser printers use RIPs to convert images that arrive in vector form (for example, text in a specified font) into rasterized and therefore printable form.
RIPs are also used to enlarge images for printing. They use special algorithms (such as error diffusion and schochastic) to provide large blow-ups without loss of clarity.
Process of copying from secondary storage (hard disk or tape) to RAM.
Refers to the ability of a computer program to refer to itself, thus repeating a set of instructions.
refresh rate
The number of times per second that the cathode ray tube (CRT) fires at each pixel. Measured in hertz (Hz), times per second. Rates below 60Hz will produce a noticeable flicker. Higher rates indicate a more stable image on the display.
A portion of high speed memory where data regarding the execution of an instruction are stored.
relational data base
A form of data base with multiple linked tables.
relational operators
In formal logic, operators which express the relationship between two expression, equal to, less than, greater than, less than or equal to, greater than or equal to, not equal to.
A measure of the precision of a monitor. The number of pixels. Usually stated as number across the screen by number of scan lines down the screen. Example: 1024x768.
Red Green Blue. The three colors used in most display devices (monitors). Requires three color values or signals to display any color.
Read Only Memory. Permanent memory within the computer (not lost when electric power is turned off). Cannot be changed, only read. ROM stores the sets of instruction that direct the computer when is first powered on. Compare to RAM.
root directory
The top or highest level directory.
The execution of a program.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
To store data to disk by copying from RAM. Note that it is a copying process.
scaling, scalar transformation
A manipulation of graphic data that results in an increase or decrease in the size of the element, depending on the scalar factor. The mathematical process is one of multiplication. The smallest scalar factor possible is zero.
1.) The order in which information is searched
2.) the conversion of images or text from paper to digital form (digitizing) for use by a computer system. Done on a scanner.
scan line
One horizontal row of pixels on a display. The number of scan lines down is a measure of the resolution of a display.
A peripheral device used to digitize text or graphic images.
Informal term for the monitor or display or CRT
To make a document appear to slide or move smoothly past the screen or window. Permits the viewing of documents larger than the screen. Controlled by arrow keys on the keyboard or by scroll arrows in windows.
screen buffer
Another term for VRAM, Video Random Access memory. Stores the data (the bit) to be displayed.
Acronym for small computer system interface. Pronounced "scuzzy," SCSI is a parallel interface standard used by Apple Macintosh computers, PCs, and many UNIX systems for attaching peripheral devices to computers. Nearly all Apple Macintosh computers, excluding only the earliest Macs and the recent iMac, come with a SCSI port for attaching devices such as disk drives and printers.
SCSI interfaces provide for faster  transmission rates (up to 80 megabytes per second) than standard serial and parallel ports. In addition, you can attach many devices to a single SCSI port, so that SCSI is really an I/O bus rather than simply an interface.
Although SCSI is a standard, there are many variations of it, so two SCSI interfaces may be incompatible. For example, SCSI supports several types of connectors.
While SCSI has been the standard interface for Macintoshes, the iMac comes with IDE, a less expensive interface, in which the controller is integrated into the disk or CD-ROM drive. Other interfaces supported by PCs include enhanced IDE and ESDI for mass storage devices, and Centronics for printers. You can, however, attach SCSI devices to a PC by inserting a SCSI board in one of the expansion slots. Many high-end new PCs come with SCSI built in. Note, however, that the lack of a single SCSI standard means that some devices may not work with some SCSI boards.
The following varieties of SCSI are currently implemented:
SCSI-1: Uses an 8-bit bus, and supports data rates of 4 MBPS
SCSI-2: Same as SCSI-1, but uses a 50-pin connector instead of a 25-pin connector, and supports multiple devices. This is what most people mean when they refer to plain SCSI.
Wide SCSI: Uses a wider cable (168 cable lines to 68 pins) to support 16-bit transfers.
Fast SCSI: Uses an 8-bit bus, but doubles the clock rate to support data rates of 10 MBPS.
Fast Wide SCSI: Uses a 16-bit bus and supports data rates of 20 MBPS.
Ultra SCSI: Uses an 8-bit bus, and supports data rates of 20 MBPS.
SCSI-3: Uses a 16-bit bus and supports data rates of 40 MBPS. Also called Ultra Wide SCSI.
Ultra2 SCSI: Uses an 8-bit bus and supports data rates of 40 MBPS.
Wide Ultra2 SCSI: Uses a 16-bit bus and supports data rates of 80 MBPS.
secondary storage
Another term for permanent memory, hard disk or tape, mass memory.
Refers to processing data one bit at a time. As opposed to parallel.
serial port
A connector or socket on the computer, capable of passing electronic data in serial fashion, one bit at a time. As opposed to a parallel port which can pass data more than one bit at a time.
1) In general, a server is a computer program that provides services to other computer programs in the same or other computers.
2) The computer that a server program runs in is also frequently referred to as a server (though it may contain a number of server and client programs).
3) In the client/server programming model, a server is a program that awaits and fulfills requests from client programs in the same or other computers. A given application in a computer may function as a client with requests for services from other programs and also as a server of requests from other programs.
Specific to the Web, a Web server is the computer program (housed in a computer) that serves requested HTML pages or files. A Web client is the requesting program associated with the user. The Web browser in your computer is a client that requests HTML files from Web servers.
The sets of instructions (programs) which manipulate data and control the functioning of the computer system.
Arrangement of data into an ordered sequence.
source code
The set of instructions, as written by a programmer, usually in a high level language.
spool, spooling
The arrangement of output in temporary secondary storage in anticipation of transfer to an output device, such as print spooling or plot spooling.
A curve calculated by a mathematical expression that connects points to produce a smooth curve.
standard input
Input which is received from the keyboard.
standard output
Output which is sent to the monitor for display.
A directory within, or below, another directory.
Transmission of data at timed intervals.
system administrator
On a UNIX system, the person (userid) which has authority to control all aspects of the computers operation.
system memory
Another term for RAM, or random access memory. Often called main memory or working memory.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
Transmission Control Protocol/Internet Protocol is the basic communication language or protocol of the Internet. When you are set up with direct access to the Internet, your computer is provided with a copy of the TCP/IP
Approximately one trillion bytes (2 to the 40 = 1,099,5116E12 ).
A peripheral devise for sending and receiving data. A dumb terminal is usually a keyboard and screen, with no local processing capability. A smart terminal has a local CPU and RAM.
TIFF (Tag Image File Format) is a common format for exchanging raster graphics (bit) images between application programs, including those used for scanner images. A TIFF file can be identified as a file with a ".tiff" or ".tif" file name suffix. The TIFF format was developed in 1986 by an industry committee chaired by the Aldus Corporation (now part of Adobe Software). Microsoft and Hewlett-Packard were among the contributors to the format. One of the most common graphic image formats, TIFF files are commonly used in desktop publishing where high quality images are important. TIFF files are "lossless" in that they retain all of the data in the original image. Thus they are often very large in size.
TIFF files can be in any of several classes, including gray scale, color palette, or RGB full color, and can include files with LZW, or CCITT Group 4 standard run-length image compression.
The use of a single key on a keyboard, which switches back and forth between two functions.
Token Ring
A type of network, developed by IBM Corporation.
A specific form of data manipulation in which a graphic element is moved, or translated, from one location to another. The mathematical process is one of addition (the existing X value plus the X differential equals the new X value).
Trojan horse
In computers, a Trojan horse is a program in which malicious or harmful code is contained inside apparently harmless programming or data in such a way that it can get control and do its chosen form of damage, such as ruining the file allocation table on your hard disk. In one celebrated case, a Trojan horse was a program that was supposed to find and destroy computer viruses. A Trojan horse may be widely redistributed as part of a computer virus.
The term comes from Homer's Iliad. In the Trojan War, the Greeks presented the citizens of Troy with a large wooden horse in which they had secretly hidden their warriors. During the night, the warriors emerged from the wooden horse and overran the city.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
A multi-user multi-tasking operating system, originally developed by AT+T. The operating system most commonly used on workstations.
The transfer of data or files from a local terminal or PC or workstation to a mainframe.
The name of a computer user, established by the system administrator. The userid becomes the owner of certain files and directories.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
Video Display Terminal. A terminal with display capability.
Video Graphics Array or Adapter. Device which connects a computer with a high resolution display.
video ram
Video Random Access Memory. Stores the bit which controls the display. Same as screen buffer and frame buffer.
A point of view, defined by an Eye Point and an Object Point, each with an X,Y and Z location in space. Independent of graphic data. The full definition of a view includes the angle of the cone of vision and the hither (near) and yon (far) clipping planes.
virtual machine
The ability of a large computer to simulate the ability of another machine.
virtual memory
The use of a portion of secondary storage (hard disk) as an extension of primary storage (RAM).
A computer program which attaches itself to another program and, at a specified condition, acts to disrupt or destroy other functions of the computer system. Knowingly creating and distributing a virus is a criminal offence.
A virus is a piece of programming code usually disguised as something else that causes some unexpected and usually undesirable event. A virus is often designed so that it is automatically spread to other computer users. Viruses can be transmitted as attachments to an e-mail note, as downloads, or be present on a diskette or CD. The source of the e-mail note, downloaded file, or diskette you've received is often unaware of the virus. Some viruses wreak their effect as soon as their code is executed; other viruses lie dormant until circumstances cause their code to be executed by the computer. Some viruses are playful in intent and effect ("Happy Birthday, Ludwig!") and some can be quite harmful, erasing data or causing your hard disk to require reformatting.
Generally, there are three main classes of viruses:
File infectors. Some file infector viruses attach themselves to program files, usually selected .COM or .EXE files. Some can infect any program for which execution is requested, including .SYS, .OVL, .PRG, and .MNU files. When the program is loaded, the virus is loaded as well. Other file infector viruses arrive as wholly-contained programs or scripts sent as an attachment to an e-mail note.
System or boot-record infectors. These viruses infect executable code found in certain system areas on a disk. They attach to the DOS boot sector on diskettes or the Master Boot Record on hard disks. A typical scenario (familiar to the author) is to receive a diskette from an innocent source that contains a boot disk virus. When your operating system is running, files on the diskette can be read without triggering the boot disk virus. However, if you leave the diskette in the drive, and then turn the computer off or reload the operating system, the computer will look first in your A drive, find the diskette with its boot disk virus, load it, and make it temporarily impossible to use your hard disk. (Allow several days for recovery.) This is why you should make sure you have a bootable floppy.
Macro viruses. These are among the most common viruses, and they tend to do the least damage. Macro viruses infect your Microsoft Word application and typically insert unwanted words or phrases.
The best protection against a virus is to know the origin of each program or file you load into your computer or open from your e-mail program. Since this is difficult, you can buy anti-virus software that can screen e-mail attachments and also check all of your files periodically and remove any viruses that are found. From time to time, you may get an e-mail message warning of a new virus. Unless the warning is from a source you recognize, chances are good that the warning is a virus hoax.
Video Random Access Memory. Another term for screen buffer or frame buffer. Memory for the monitor or display device. Stores the information (the bit) to be displayed.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
warped polygon. See degenerate polygon.
A section of a display screen within which a program or process can be executed.
word wrap
In word processing, the automatic truncation of one line and placement of text on the next line. Introduces a "soft carriage return" control character.
working memory
Yet another term for RAM, or random access memory. Often called system memory or main memory.
work station.
A powerful computer system characterized by: 1.) a powerful 32 bit high speed CPU; 2.) large amounts of mass memory; 3.) large size high resolution monitor and 4.) use of the UNIX operating system.
A self-replicating virus that does not alter files but resides in active memory and duplicates itself. Worms use parts of an operating system that are automatic and usually invisible to the user. It is common for worms to be noticed only when their uncontrolled replication consumes system resources, slowing or halting other tasks.
The copying of data from primary storage (RAM) to secondary storage (hard disk or tape).
What You See Is What You Get. In word processing, the display on a monitor of a document in the same form it will be if printed.
left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
blackdot.gif (799 bytes)
The yon or far clipping plane in a view. An imaginary plane, perpendicular to the line of site. Graphic data located beyond the yon plane will not be displayed.
left-arrow.gif (166 bytes)Return to beginning of glossary
The preferred term is listed first:

primary memory, main memory, working memory, current memory, active memory, RAM, DRAM

display, monitor, CRT, screen

secondary memory, disk, diskette, tape, CD-ROM (they may be physically different but they are logically treated the same way)

hard disk, hard drive, fixed disk

diskette, floppy disk, floppy,

VRAM, Video Ram, screen buffer, frame buffer

FAX, facsimile

CAD, CADD: Computer Aided Drafting, Computer Aided Design, Computer Aided Drafting and Design

e-mail, email, electronic mail

left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
The following symbols are used in many operating systems, particularly in DOS and DOS derivatives such as Windows 95/98, Unix. Linux and WindowsNT:

NOTE: Many application programs follow the same conventions, typically the *. However, many application programs do not follow the same conventions for precisely the same reason. This is particularly true in word processing programs, text editing programs and command language based programs where distinguishing between command content and command syntax is important.

* (Asterisk) Global string variable, variable for any character string, in UNIX and DOS.
Example: *.gr =

? (Question mark) Single character variable, in UNIX and DOS.
Example: file?.gr =

/ (Forward slash) Root file and delimiter, in UNIX
Example: /dirname/subdirname/filename

\ (Backward slash) Root file and delimiter, in DOS
Example: \dirname\subdirname\filename

. (Dot) 1. The current directory, in UNIX and DOS.
Example: cp \dirname\filename .  means copy the file named filename from the subdirectory dirname to the current directory
2. delimiter (DOS) between filename and filetype
Example: filename.filetype floor01.dwg

.. (Dot dot) The parent directory, in UNIX and DOS.
Example: cd ..   means  change the current directory to the parent directory

| (Vertical line or double vertical line) Pipe, in UNIX and DOS. Redirects output from one process to be the input of another process.
Example: ls *gr | more

left-arrow.gif (166 bytes)Return to beginning of glossary


Kilo, mega, giga, tera, peta, and all that

Kilo, mega, giga, tera, and peta are among the list of prefixes that are used to denote the quantity of something, such as, in computing and telecommunications, a byte or a bit. Sometimes called prefix multipliers, these prefixes are also used in electronics and physics. Each multiplier consists of a one-letter abbreviation and the prefix that it stands for.

In communications, electronics, and physics, multipliers are defined in powers of 10 from 10-24 to 1024, proceeding in increments of three orders of magnitude (103 or 1,000). In IT and data storage, multipliers are defined in powers of 2 from 210 to 280, proceeding in increments of ten orders of magnitude (210 or 1,024). These multipliers are denoted in the following table.

Prefix Symbol(s) Power of 10 Power of 2
yocto- y 10-24 *  --
zepto- z 10-21 *  --
atto- a 10-18 *  --
emto- f 10-15 *  --
pico- p 10-12 *  --
nano-   n 10-9 * --
micro- m 10-6 *  --
milli- m 10-3 *  --
centi- c 10-2 *  --
deci- d 10-1 *  --
(none) -- 100 20


D 101 *  --
hecto- h 102 *  --


k or K ** 103 210
mega- M 10 220
giga- G 10 230
tera- T 1012  240
peta- P 1015  250
exa- E 1018 *  260
zetta- Z 1021 *  270
yotta- Y 1024 *  280

*Not generally used to express data speed

** k = 103 and K = 210

Examples of quantities or phenomena in which power-of-10 prefix multipliers apply include frequency (including computer clock speeds), physical mass, power, energy, electrical voltage, and electrical current. Power-of-10 multipiers are also used to define binary data speeds. Thus, for example, 1 kbps (one kilobit per second) is equal to 103, or 1,000, bps (bits per second); 1 Mbps (one megabit per second) is equal to 106, or 1,000,000, bps. (The lowercase k is the technically correct symbol for kilo- when it represents 103, although the uppercase K is often used instead.)

When binary data is stored in memory or fixed media such as a hard drive, diskette, ZIP disk, tape, or CD-ROM, power-of-2 multipliers are used. Technically, the uppercase K should be used for kilo- when it represents 210. Therefore 1 KB (one kilobyte) is 210, or 1,024, bytes; 1 MB (one megabyte) is 220, or 1,048,576 bytes.

The choice of power-of-10 versus power-of-2 prefix multipliers can appear arbitrary. It helps to remember that in common usage, multiples of bits are almost always expressed in powers of 10, while multiples of bytes are almost always expressed in powers of 2. Rarely is data speed expressed in bytes per second, and rarely is data storage or memory expressed in bits. Such usages are considered improper. Confusion is not likely, therefore, provided one adheres strictly to the standard usages of the terms bit and byte.

left-arrow.gif (166 bytes)Return to beginning of glossary
blackdot.gif (799 bytes)
Link to Syracuse University home page Send email to:
Last update: November 06, 2002. Copyright 2003 Bruce M. Coleman
No text, images or content on this page may be copied or linked to without the author's express written permission.