Computer Science

Cache
A place where data is stored to avoid having to read the data from a slower device. Copies of frequently used disk sectors are stored in RAM so that they can be accessed without accessing the hard disk.

CAM
Common Access Method

Carrier
Companies contracted to carry our data over long distances.

CD ROM
Compact Disk Read Only Memory - Like an audio compact disk, but contains computer data. Most computers can only read a CD ROM but new, equipment is available for recording them.

Cellular Networking
A form of mobile computing.

Certificate Authority
An issuer of Security Certificates used in SSL connections.

CGI
Common Gateway Interface - A set of rules that describe how a Web Server communicates with another piece of software on the same machine, and how the other piece of software (the "CGI program") talks to the web server.

cgi-bin
The most common name of a directory on a web server in which CGI programs are stored. The "bin" part of "cgi-bin" is a shorthand version of binary.

Chat Room
A place on the Internet where people go to "chat" with other people in the room. The rooms are usually organized by topic. When you're in a Chat Room you can view all of the conversations taking place at once on your screen. You can also get into a private chat room where only you and one or two others may talk.

Chip
The ultimate integrated circuit that contains the complete arithmetic and logic unit of a computer. See Microprocessor

Chip Set
A group of computer chips or ICs (integrated circuits) which, when working in harmony, manage and control the computer system. This set includes the CPU and other chips which control the flow of data throughout the system. Typical chip sets consist of a bus controller, a memory controller, data and address buffer and a peripheral controller.

CHS
Cylinder Head Sector

CISC
Complex Instruction Set Computer - A computer with many different machine language instructions.

Class A IP Address
IP Address used by very large networks, such as IBM, GM, or DEC.

Class B IP Address
IP Address used by medium-sized networks, such as Microsoft; these are all in use at the present time.

Class C IP Address
Class C IP addresses are used for smaller networks that do not exceed 254 hosts.

Client
The computer that connects to the network and uses the available resources provided by the server. User computer "being served" by another computer, called a server. A Web Browser is a specific kind of Client.

Client Software
Software used by the client.

Clock
A conductor located in the CPU for the purpose of timing and synchronizing commands. The conductor is pulsed with voltage, when the CLK has voltage this is called a "clock cycle". All switching activity in the computer occurs while the clock is sending a pulse and between pulses the devices are allowed to stabilize. Establishes the maximum speed at which the processor can execute commands.

Clock Speed
Measured in Megahertz (MHz) or millions of cycles per second. It is the speed at which a clock can cycle, or how fast a CPU can execute a command.

Clocking
The method used by the NIC to count and pace the number of signals that it sends and receives.

Cluster
To combine a set of contiguous sectors and treat them as a single unit.

CMOS
Complimentary Metal-Oxide Semiconductor - A chip that gets its name from the way it is manufactured and not the information it holds. Unlike other ROM chips, CMOS chips store data that is read by the BIOS to complete the programs needed to talk to changeable hardware.

CMOS Battery
Prevents unique information about the set-up of the computer from being lost when the power is turned off. Also maintains the external clock time (not to be confused with the CPU's clock).

Coaxial Cable
Made of two conductors that share the same axis. The center is a relatively stiff copper wire encased in insulating plastic. A wire mesh tube around the insulation serves as shielding. The outside is a tough insulating plastic tube.

Code
A way of representing information on a machine or in some physical form so that the information can be placed on the external data bus to be read by all devices.

co-location
Most often used to refer to having a server that belongs to one person or group physically located on an Internet-connected network that belongs to another person or group. Usually this is done because the server owner wants their machine to be on a high-speed Internet connection and/or they do not want the security risks of having the server on their own network.

COM1, COM2
Communication Port. The file names assigned to the first two serial ports on a PC.

Concentrator
Same as a hub.

Cookie
The most common meaning of "Cookie" on the Internet refers to a piece of information sent by a Web Server to a Web Browser that the Browser software is expected to save and to send back to the Server whenever the browser makes additional requests from the Server.

Cooperative Multitasking
A form of multitasking, in which it is the responsibility of the currently running task to give up the processor, to allow other tasks to run.

Coprocessor
A separate circuit inside a computer that adds additional functions to the CPU or handles extra work while the CPU is busy.

Counter
A number on many web pages that will count the number of hits or count the number of times the page has been accessed. Basically, it counts the number of people that have visited that page.

CPU
Central Processing Unit - This is the part of a computer where arithmetic and logical operations are performed and instructions are decoded and executed. It controls the operation of the computer.

Cracker
A person who breaks into a site through a computer's security. Basically, the same thing as a Hacker, a Cracker is sometimes considered to be more malicious and destructive.

CRC
Cyclic Redundancy Check, or Cyclic redundancy Code, is a number derived from, stored, or transmitted with a group of data in order to detect data corruption.

Crosstalk
The signal bleed that occurs between individual wires in a cable.

CRT
Cathode Ray Tube - The main component of a monitor, one end of the tube is a very slender cylinder containing an electron gun(s). The fatter end is the display screen.

CSMA/CA
Carrier Sense Multiple Access with Collision Avoidance

CSMA/CD
Carrier Sense Multiple Access with Collision Detection

CSNW
Carrier Sense NetWare

Cyberspace
Term used to describe the Internet; the term was coined by science-fiction novelist William Gibson in 1984 in Neuromancer.