A means of storing information so it can be retrieved quickly. When you visit a web site, your browser cache temporarily stores the site's data -- text, graphics, sounds, and URLs -- on your computer's hard drive. That way, when you visit the site again, you don't have to go through time-consuming Internet access. But caching isn't just for the Internet; you can cache data within your computer. Example: Access to your hard drive (aka hard disk) is slower than access to RAM (Random Access Memory -- the computer's short-term memory), so disk caching stores data from your hard disk in faster RAM.


Cookies, aka HTTP cookies or Web cookies, are small data files that are automatically entered into your computer's hard drive by some web sites you visit. They enable those web sites to track such things as your passwords, other web sites you've connected with, and the dates when you last looked at certain sites. Cookies have been criticized for intruding on computer users' privacy. There are anti-cookie functions available for personal computing, but some web sites, such as those that sell products, won't work if your computer won't accept their cookies.

Common Gateway Interface (CGI)

A computing standard that sets the rules for connecting, or interfacing, your personal computer with a Web server. The CGI enables the server to respond to your request to connect to a web site and communicates information back to whatever computer software that you are using (called an external program). CGI can be slow on busy web sites. An alternative is the API, or application program interface, a more complex technology, but one that works more directly with the Web server, so it's faster.

Central Processing Unit (CPU)

The CPU -- a highly complex silicon chip ranging from the size of a matchbook to the size of a wallet -- is your computer's brain. Along with memory and input-output function, it is one of the three key components of a computer. The CPU takes requests from various software applications and then processes them so that the computer can perform the actions, known as operations, that you have requested. The faster your CPU, the more operations it can execute per second, and the faster things happen: Computer games play more smoothly, spreadsheets calculate more quickly, etc. Sometimes the term CPU is also used to describe the whole box that contains the chip along with the motherboard, expansion cards, disk drives, power supply, and so on. Both uses are widespread, but only the first -- the chip -- is really accurate.

Comma-Separated Values

CSV (comma-separated values) is a method of saving information in a plain text file that can be imported into any type of spreadsheet or database software. The importing software will "separate" the information into a new field each time it reads a comma. Note: The separating character does not have to be a comma. You may choose another unique character, such as a symbol. In this case, CSV stands for character-separated values.

Coder/Decoder or Compression/Decompression Algorithm (Codec)

True to their name, codecs are used to encode and decode (or compress and decompress) various types of data -- particularly sound and video files that would use up inordinate amounts of space on your computer. Codecs typically convert lengthy analog signals into compressed digital signals, such as MPEG for video and Real Audio for audio. Codecs can be used with either streaming (live) or file-based content.