C

CDR (CD-recordable disc)
A CD that allows you to record on it.

Central Processing Unit (CPU)
The computational and control unit of a computer; the device that interprets and executes instructions. The CPU has the ability to fetch, decode, and execute instructions and to transfer information to and from other resources over the computer�s main data-transfer path, the bus.

character
A letter, number, punctuation mark, or other symbol or control code that is represented, to a computer, by one unit (1byte) of information. A character is not necessarily visible, either on the screen or on paper; a space, for example, is as much a character as is the letter "a" or any of the digits 0 through 9.

character matrix
The total number of horizontal and vertical spaces desired per character.

character set
A collection of characters, e.g. A to Z, 0 to 9, punctuation marks, mathematical symbols, graphics and others. Each character in a set is represented by a binary value (sometimes called a bit pattern). Different character sets have different binary values for characters. Examples of character sets are ASCII, EBCDIC And Kangi.

chip
Any electronic device built into a wafer or 'chip' of silicon. A processor or memory unit in any intelligent device. The 'processor' in any device is often referred to as the 'chip.'

click
To press and release a mouse button once without moving the mouse. Clicking is usually performed to select or deselect an item or to activate a program or program feature.

client
Any intelligent device linked in a network to a server. A client can undertake its own computing using data provided by the server.

client/server
A system in which a number of 'client' devices (usually PCs or workstations) are connected via a network to one or more data storage and retrieval machines known as 'servers'. When a user runs a program, their machine (the client) passes any requests for data (along with selection criteria and sorting instructions) to servers. Servers generally hold information in a database format, and should be capable of filtering out the required elements, putting them in order as instructed by their clients, and thus sending just the necessary amount of information back across the network. When the client machine receives the requested information, it processes it according to software held in its own memory. Another useful but more technical description of client/server is 'running software' in parallel on multiple nodes (many PCs operating at the same time on one Network), whereas mainframes and minis run software on one node only (the host machine). Client/server architecture is being increasingly adopted as a means of maximizing the effectiveness of multi-user systems where a number of different applications need to be running simultaneously. In control and telecommunications systems, the term used instead of 'client/server' is 'distributed processing'.

co-processor
A processor which assists the main processor (CPU) by performing certain ancillary functions which can greatly increase the speed of operation, often the co-processor executes the decode instructions of the machine cycle.

coaxial cable
A cable used to connect two computers together for networking.

cold boot
A startup process that begins by turning on the computer's power.

color balance
The ability of the monitor to show and maintain the same color when switching or varying the intensity of the screen.

command
An instruction to a computer program that, when issued by the user, causes a certain action to be carried out. Commands are usually either typed at the keyboard or chosen from a menu with the keyboard or with an alternative input device such as a mouse.

Common Object Request Broker Architecture (CORBA)
A standard from the Object Management Group (OMG), providing interface definitions and protocols between objects. Competes with OLE from Microsoft.

communications server
In networks, a dedicated system that manages communications activities for other computers.

compatible
Programs, data files, devices or systems that are able to work together and understand the same commands, formats and language as one another.

compiler
A program that converts source code to object code which can be linked to produce an executable program.

compression
Often called Zipping: Making a reduced-size copy of a disk file using compression programs. Most data or programs include a significant proportion of blank spaces or other repeated bytes - each one contributing to the amount of space occupied by that file on disk. A compression program copies non-repeated bytes in the normal way. However, when it detects repetitions it counts the number of repeats. Then instead of storing that number of bytes, it writes a code indicating the repeated byte and a code for the number of repetitions. These codes normally take only a tiny fraction of the original space, so that the compressed copy is often only 25 percent the size of the original. Compression is very useful for transferring files between machines, either via telephone lines or diskette. Unfortunately, software cannot normally use data or program files in the compressed state. When a compressed file needs to be restored to normal size, it is decompressed or 'unzipped' using another program which reverses the compression procedure. Examples of compression software are PKZIP, Compress, GZIP and WINZIP (for Windows).

computer
Any machine that does three things: accepts structured input, processes it according to prescribed rules, and produces the results as output.

computer based training
Interactive training using computer-based learning systems known as courseware.

CONFIG.SYS
A special text file that controls certain aspects of operating-system behavior in MS-DOS and OS/2. Commands in the CONFIG.SYS file enable or disable system features, set limits on resources (for example, the maximum number of open files), and extend the operating system by loading device drivers that control hardware specific to an individual computer system.

configuration management
Documenting, recording and releasing the elements of a complete suite of software using version control. Controlling the configuration of any complex system; see Configuration Management of Client/Server.

Configuration Management of Client/Server
In Client/Server computing (as opposed to Terminal/Host computing), processing can happen anywhere - on the clients, on the application servers (Three-Tiered Systems), or on the Data Servers (stored procedures). The balance and control of the distribution of processing is a major factor in the success of a Client/Server Network. Two tools are necessary for effective Configuration Management: 1. Central Inventory - Identifies all software items, their type, where used and the upward (to servers) or downward (to clients) dependency. 2. Central Repository - Holds all application software programs and their revisions. The repository also holds the software tools for version control, configuration mapping and change control for all new software releases.

context sensitive
In Windows, it is possible to write application software which detects where the mouse cursor is positioned on the screen and to bring up menus, (normally by clicking the right hand mouse button) that relate to information displayed at that point on the screen.

control key
A key that, when pressed in combination with another key, gives the other key an alternative meaning.