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C++ - A modern version of the C programming language. Used extensively in UNIX based systems, but also found on Personal Computers. It is used for it's compactness and speed of execution of the final produced compiled code. Considered difficult to use and maintain compared to other object orientated languages, but it is still favoured by many software houses. Two main graphical versions are available from Microsoft and Borland. See also UNIX, compiler and object orientated programming.

Cache - An area of fast memory where programs and data can be stored and repeatedly retrieved from which would be quicker than the slower device or memory where it would normally reside. Cache memory can reside in processors, hard discs and just about any other device where it is anticipated that speed gains could be had when repeatedly reading from a slower device. See also memory, devices, processors and hard discs.

Celeron - The brand name of a processor made by Intel. Originally released with a 66Mhz bus as an inexpensive Slot 1 type processor to rival Cyrix/IBM and without any cache memory on the chip. Intel quickly realised this was a mistake and quickly added 128k of level 2 cache memory running at the full bus speed which is unlike it's bigger brother the Pentium II. The full bus speed made up for any lack of memory cache it possessed and some say that it is nearly as quick as a Pentium II anyway but much cheaper. Modern Celeron's since the summer of 1999 have been shipping in socket 370 format to save space on the motherboard. See also Intel, bus, socket 370, Pentium II, Cyrix/IBM and cache memory.

CDFS - Compact Disc Filing System. The filing system used to store data on CD's. See also CD.

CD-ROM - A permanent way of writing large amounts of data (up to 650Mb) to a single sided disc platter that can only be read from. A very low power laser is used in a CD-Drive to read small indentations in the disc surface recreating the 0's and 1's that make up the data image from the differing angles of reflection . This could be used for backup purposes or for distributing programs and data. The technology is also known as CD-R or CD-ROM's for their Read Only Memory attributes, although the M in ROM adds to the confusion as there are no memory chips on the disc. CD's can be created either by stamping in a press for mass distribution or in a special CD writer device that can write a single CD disc at a time.

CD-R - A CD writer device (also known as a CD-R device) relies on a more powerful laser to "melt" the disc surface, and so the process is called "burning a CD". This CD surface can only be burned once, however, it is possible to use only a part of the surface and re-burn the disc using the unused part. See also CD-ROM, and also CD-RW for reusable CD discs.

CD-RW - Advances in technology allow a special read and write CD disc to be used in a specially prepared CD drive aided by a more powerful laser device to "melt" the surface. A powerful magnet is also employed to create the 0's and 1's on the disc surface. CD-RW discs can be written to approximately 1000 times and are known as CD-RW. CD-RW drives are slower than CD-R writers as they first have to "melt" the surface of the disc to erase previously stored data. CD-RW drives can read and write CD-R drives too, but cannot erase a CD-R disc. See also CD-ROM.

CGA - Colour Graphics Adapter. An archaic colour version of a black and white graphics adapter. The term is no longer used as all graphic cards are colour. See also Graphics Adapter.

CGI - Computer Gateway Interface. A method in which an Internet browser can communicates with other Internet services on a web server. For example:- a web database or search engine. See also Internet, browser, Database and Search Engine.

Character - A single item of text information, i.e. the letter "A" or "7" or ":" etc. Characters can vary depending upon the operating system of the computer system and the global region due to the language used in that country. See also Character Sets, String and Data Types.

Character Sets - These are the complete set of binary representations of the text characters that can be used in the computer system. Each text character is represented by a number in the range that can fit into a byte. Two common character sets are ASCII and EDCDIC. Each character of text usually takes up a byte of data in the computers memory or on backing store. A character set should not be confused with a font. See also byte, font, ASCII and EBCDIC.

Chipset - See also Motherboard.

CHKDSK - The command is short for Check Disk. A program used to check that the files stored on that disc are in fact intact and have not become corrupted in anyway. The parameter /F is used to fixed any errors found. Windows 95/98 as an updated Scandisk program, and NT uses a special version of CHKDSK for use on NTFS partitions. See also Hard Disc, Scandisk, NT, NTFS, Windows and parameter.

Circular Reference - A reference to a cell in a spreadsheet application that reference this first cell. For example:- See also Circular Reference.

Client/Server - This is the process of splitting the job of retrieving data over a network between your client machine and the server machine you are logged into. This allows a slower inexpensive computer to be used as the client, enabling more clients can be purchased. The raw processing power of the server is much higher than the client and so is able to service the client requests much quicker. Completed requests can be held in memory centrally by the server in case the same request is repeated. The resultant reply can be repeated to another client much quicker and so has significant advantages. Client server architectures are known as a two tier system. If the server is employed as a local departmental server and must itself send a request to a central data warehouse, this is known as a three tier system. See also server and data warehouse.

Clipboard - An an area of memory set aside in Windows which allows for the storage and transfer of data from one application to another. A user can "cut and paste" the data. See also Application.

Clock Speed - The speed at which the computers CPU is operating at. This is usually some multiple of the computers motherboard bus speed multiplied by the clock multiplier. For example, a computer running at 500Mhz may have a motherboard bus speed of 100Mhz. The clock multiplier may be x5, giving a total CPU clock speed of 500Mhz. See also CPU, Motherboard and Bus Speed.

Cluster - A number of consecutive sectors in a track on a disc that are said to be a cluster of sectors or just "cluster". Also known as an allocation unit. An allocation unit can typically have 512 bytes on a floppy disc and more in a hard disc. See also Track, Sector, FAT and FAT32.

CODEC - Compressor Decompressor. A device driver that allows audio and video data to be stored more efficiently by squeezing (compressing) it so it takes up less disk space or network bandwidth. To listen (or view) it is necessary to expand it again. See also Disc, Network and Bandwidth.

COM - Short for Communication Port. In a personal computer, up to 4 communication ports can be attached and simple devices like modems, mice and small dot matrix printers can be used. The speed at which communication can take place is measured in baud and is usually performed in a serial fashion, i.e. a single bit if data at a time. This type of communication with a device or another computer is therefore only suited where speed is not considered an important factor. See also baud, modems and serial port.

COM - Component Object Model. Integral to OLE and defining the standards that server applications will use to create and interact with container applications when they deal with these objects. See also Client/Server, OLE, Application and Container Application.

COM - Short for command. A type of file containing an operating system program that can be loaded in from disc and executed from a command prompt. For example:- edit.com. You would type "edit my_file.txt" and use the edit program as if it were an operating system command. See also File, Disc, Operating System, Program and Execute.

Compiler - A program that is used as a method of translating a human readable text program into the binary machine code form that can be read and understood by a processor, i.e. in to its own native binary language. This has only to be performed once when the program is created. The resultant code can be read by the processor as many times at it is required without any further translation taking place. The is the method of creating software applications. It is inherently quicker than an interpreted language where the human readable text program is passed through an interpreter line by line each time the program is required. The time overhead is in the line by line translation. See also Interpreter, software and processor.

Compression - The method of substituting less bits (or bytes) than the original data message without loosing any meaning for storage or transmission purposes. Compression is popular when connected to another computer via modem, for example:- to your ISP for an Internet connection, which will enable a slow link to transfer more data than it could possibly without the use of compression. Both the transmitting and receiving ends need to agree on a method of compressing and decompressing the data. Modern modems perform this agreement automatically and so is hidden from the user. Common agreed methods of compression are MNP5, V.42bis, V.90 etc. See also Bits, Bytes, Modem, ISP and Internet.

Computer - The name originates from the days of manual clerical financial numeric calculation where many men were employed to compute the financial and tax calculations for companies by a firm of accountants. The first computers were mechanical weaving devices, so the modern name could quite easily have been "an electronic loom". The first electronic computers were employed in the field of encryption and code breaking during World War 2. The first general purpose electronic device was used after the war to perform simple mathematics calculations and so derived the name from the first meaning above. General purpose computers after this event just became known as computers.

Container Application - The application that you use to store a linked or embedded OLE object created with a server application. Also known as the client application. See also OLE, Application and Client/Server.

Control Panel - The Control Panel is a program the can be run in a Microsoft Windows based computer that allows the user easy access to view and/or change the computers settings. See also Microsoft and Windows.

CPU - Central Processing Unit, or just processor. The device that executes program code on a computer. There may be more than one CPU in a computing device.

Cross Linked Cluster - A disc cluster has been assigned to, or a reference pointer is pointing to a different file causing a disc or file allocation error. Recovery action would be to run your operating systems disc recovery tools. See also Disc, Cluster, File, FAT and Operating System.

Cyrix/IBM - An inexpensive socket 7 design of Intel Pentium clone. Ideal for desktop computers where cost is a significant consideration in build design. See also socket 7, Intel, Pentium and Desktop.

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