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C
An advanced programming language used for programming advanced computer applications.

C++ (C Plus Plus)
The same as C with added object-oriented functions.

C# (C Sharp)
A Microsoft version of C++ with added Java-like functions.

Case Sensitive
A term used to describe if it is of importance to use upper or lower case letters.

Cache
In web terms: A web browser or web server feature which stores copies of web pages on a computer's hard disk.

Chat
An on-line text-based communication between Internet users.

CGI (Common Gateway Interface)
A set of rules that describes how a CGI program communicates with a web server.

CGI Bin
The folder (or directory) on a web server that stores CGI programs.

CGI Program
A small program that handles input and output from a web server. Often CGI programs are used for handling forms input or database queries.

Cinepac
A codec for computer video.

Client
See Web Client.

Client/Server
In web terms: The communication and separation of workload between a web client and a web server.

Click
In web terms: A mouse click on a hyperlink element (such as text or picture) on a web page which creates an event such as taking a visitor to another web page or another part of the same page.

Clickthrough Rate
The number of times visitors click on a hyperlink (or advertisement) on a page, as a percentage of the number of times the page has been displayed.

Codec (Compressor / Decompressor)
Common term for the technology used for compressing and decompressing data.

Communication Protocol
A standard (language and a set of rules) to allow computers to interact in a standard way. Examples are IP, FTP, and HTTP.
Learn more about Communication Protocols in our TCP/IP tutorial

Compression
A method of reducing the size (compress) of web documents or graphics for faster delivery via the web.

Computer Virus
A computer program that can harm a computer by displaying messages, deleting files, or even destroying the computer's operating system.

Cookie
Information from a web server, stored on your computer by your web browser. The purpose of a cookie is to provide information about your visit to the website for use by the server during a later visit.

ColdFusion
Web development software for most platforms (Linux, Unix, Solaris and Windows).

CSS (Cascading Style Sheets)
A W3C recommended language for defining style (such as font, size, color, spacing, etc.) for web documents.
Learn more about CSS in our CSS tutorial

Cache
To store on a computer user's hard disk a local copy of a web page accessed via the Internet. The web browser compares the cached copy of the page to the original, and if there have been no changes, the browser will use the cached copy rather than reloading the page onto the client, saving processing and download time. Also refers to a web site's database generating static copies of frequently requested dynamic pages, reducing processing time.
Channel
A dynamic information-delivery source. A web site becomes a web channel when it dynamically broadcasts its content to users who have expressed an interest in receiving that information. Users can select channels they want to receive so they do not have to type the address for each site every time they want that information. It's ready for them when they want it, stored in a cache for easy viewing offline. See also Push.
Chat
A feature that lets you talk with other computer users in real-time online sessions.
Client
Computer hardware or software used by an end user on a computer network or the Internet to query a remote server. A web browser is an example of client software.
Client-Server
A computing network in which the functions are divided between clients (or personal computers or terminals), and servers that store, process, and transmit the information.
Client-Side Program
A computer program that is downloaded from a server and executed or run using the end user's computer hardware. Java and JavaScript are examples of client-side programs.
Commands and Filters
Commands and filters allow users to prioritize and organize incoming email messages and discussion group postings.
CGI (Common Gateway Interface)
A server-side communication standard supported by all web servers for accessing external programs. Since HTML allows only one-way communication from the server, which is read by the web browser or client, CGI permits communication and interaction from the client to the server for two-way, dynamic web pages.
Cookie
A unique string of letters and numbers that the web server stores in a file on your hard drive. This method is used by web designers to track visitors to a web site so the visitors do not have to enter the same information every time they go to a new page or revisit a site. For example, web designers use cookies to keep track of purchases a visitor wants to make while shopping through a web catalog. Cookies may work through a single visit to a web site, such as when tracking a shopping trip, or may be set to work through multiple sessions when a visitor returns to the site.

C/C++

Popular programming languages (C++ includes objects) that can be used to create server programs that run after compilation. C and C++ were not designed specifically for web programming, but they can still be useful, especially because mature compilers producing very fast code and large code libraries already exist.

Cable Modem

A cable modem is used for connecting to the Internet using the cable TV infrastructure. It offers high speed Internet access.

Cascading Style Sheets (CSS)

A style-sheet determines how the HTML document is displayed by the browser. The current version of CSS is version 2 (CSS2).

CCIT

Comite Consultatif International Telegraphique et Telephonique (International Telegraph and Telephone Consultative Committee). International telecommunication standards body.

CERN

(Conseil Europeen pour la Recherche Nucleaire) A nuclear research laboratory where the World Wide Web was invented.

Certificate

Digital ID used for SSL transactions. It includes owner's public key, the name of the owner, the issuer, hostname, and the expiration date.

Certificate Authority

A company trusted by a browser maker that issues digital certificates that are supposed to guarantee that the company is what it claims to be for use in encrypted digital transactions though SSL. Verisign is the biggest certificate authority.

CGI

Common Gateway Interface. A standard for interfacing web servers with an executable application. A CGI program can be written in any language like Perl or C/C++ and it is often stored in a special directory like /cgi-bin. CGI is often used to process data from HTML forms.

cgi-bin

A directory on the server where the executable CGI scripts reside.

Channel Definition Format (CDF)

A way of defining the server-push channels for accessing frequently changing web content.

CHAP

(Challenge Handshake Authentication Protocol). An authentication protocol used in PPP protocol. Uses a username and a password.

Client

A computer program that requests a service from the server program, usually over the network.

Client/Server

A network architecture where a system is divided into two parts: the client and the server.

clustering

Connecting many computers and making them appear as one machine. This is done to increase reliability and performance.

Co-location (colo)

Putting a web server in a dedicated facility that provides high-speed Internet connection, security, environment, backup power, and technical support. Unlike the dedicated server, the client controls both hardware and software.

Cobalt RaQ

Server appliance made by Cobalt specifically for hosting companies. Newest RaQs are Linux-based and provide an easy-to-use interface. RaQs have no features that can't be had in a regular Linux box but they offer pre-installed programs and Cobalt's support. Here is the discussion forum for RaQs.

ColdFusion

ColdFusion is an easy to use server-side scripting language developed by Allaire. It comes with ColdFusion Studio, a visual IDE. Here is Allaire's ColdFusion page. Other popular server-side scripting languages are ASP. Perl, PHP, TCL, Python, and JSP.

command-line interface

The opposite of the GUI (Graphical User Interface). A way of interacting with a computer system using the keyboard and a text-only display. Usually more powerful, but less user-friendly thatn a GUI.

Control Panel

Control panel included in web hosting packages is an online web-based application that allows you to easily manage different aspects of your account. Most control panels will let you upload files, add email accounts, change contact information, set up shopping carts or databases, view usage statistics, etc.

Cookie

A Cookie is a piece of data that is saved in the user's browser by the web server. It is used to customize user's browsing experience.

CPU

Central Processing Unit. The most important part of the computer.

Crawler

Also known as spider, an automated software that retrieves webpages and follows the hyperlinks contained in them. Used to generate indexes used by search engines.

CD-ROM
Compact Disk-Read Only Memory; an optical disk from which information may be read but not written.
CD-R or Compact Disk-Recordable
Refers to computer peripheral disk drives that allow the user to record content on to a blank compact disk.
Client
A computer that has access to services over a computer network. The computer providing the services is a server. Note: in an X-11 environment, the meanings of client and server are reversed.
Client-Server Architecture
An information-passing scheme that works as follows: a client program, such as Mosaic, sends a request to a server. The server takes the request, disconnects from the client and processes the request. When the request is processed, the server reconnects to the client program and the information is transferred to the client. This architecture differs from traditional Internet databases where the client connects to the server and runs the program from the remote site. Note: in an X-11 environment, the meanings of client and server seemingly are reversed.
Configuration
This is a general-purpose computer term that can refer to the way you have your computer set up. It is also used to describe the total combination of hardware components that make up a computer system and the software settings that allow various hardware components of a computer system to communicate with one another.
Configure
The act of changing software or hardware actions by changing the settings.
CyberMall
A term commonly used to describe an electronic site shared by a number of commercial interests.
Cyberspace
A term coined by William Gibson in his novel "Neuromancer" to refer to a near-future computer network where users mentally travel through matrices of data. The term is now used to describe the Internet and the other computer networks.