Internet Dictionary
Click on a letter to see the relevant terms: A B C D E F G H I J K L M N O P Q R S T U V W Z

Cable modem Unlike a data modem that works with ordinary phone lines, a cable modem works with the existing cable TV system currently serving millions of homes. The typical data modem of today has a speed of 28.8 Kbps. The typical cable modem of tomorrow will have speeds of 30 Mbps.

Cache Pronounced "cash", this refers to storing data in a faster memory than it is already in. Here are two examples. First, the RAM in your computer works a lot faster than your hard disk. Part of the RAM is usually set aside as a cache for storing data that is frequently accessed from the hard disk. This way, the computer can retrieve the data from the faster cache instead of the slower hard disk. Here's another example of a cache. Your hard disk works a lot faster than the Internet. A typical browser will set aside some hard-disk space as a cache for storing data that is accessed from the Internet. Once on your hard disk, the browser can retrieve the data a lot faster. For instance, the first time you download this glossary, it may take a minute or more. After that, it will be in a cache on your hard disk, where subsequent accesses are much faster.

CCITT Consultative Committee for International Telephony and Telegraphy. A United Nations organization that recommends standards for international data communications. The name has recently been changed to ITU, which stands for International Telecommunications Union.

Checksum A checksum is a calculated value using the bytes of a file that can be later used to see if the file has changed. There is more than one way to calculate a checksum. The simplest checksum is to count the number of bytes in a file. Since some viruses replicate by adding bytes to a file, a simple virus check is to count the number of bytes in a file. An infected file has more bytes than it should have.

Child web Big complicated web sites need to organize their material like chapters in a book. The root web is like the front matter of the book and the child webs are like chapters. In terms of disk storage, the root web is stored in a directory called the root directory, and child webs are stored in subdirectories of this root directory.

Client The Internet is based on the server-client model. The idea is that some computers act like servers, while others acts like clients. The server is a computer that someone uses to store pages of information. The client is a computer that someone else uses to download those pages.

Com Domain names often end with abbreviations like com, edu, gov, mil, etc. to indicate the type of organization hosting the server. Com is the abbreviation for commercial and is used after the period (pronounced dot) in a domain name. For instance, a domain name like malvino.com indicates that the organization named malvino is a commercial enterprise.

Compiler A program that converts a high-level program like BASIC into machine language. For instance, when a BASIC program is compiled, every line in the program is changed into machine language (strings of 1's and 0'). The new machine-language program can then be executed by the computer.

Congestion This occurs when there's too much traffic on the communication path. Anyone who's used the Internet for a while has experienced congestion. You have congestion if web sites are very slow in responding, or your ISP's phone number is busy, or a network-down message appears, or a DNS cannot find an existing web site, or a message says your computer is at fault when it isn't, etc.

Cookie A little bit of Java code that some web servers store on your hard disk. Cookies are used to track people. When you visit a web site, a cookie-equipped server will transmit a cookie to your PC. The cookie will build as you move around the web site. Some web sites keep detailed records of who you are and where you've been. If you're using Netscape Navigator 3 or higher, you can choose to be alerted about a cookie invasion. You can then accept or decline the cookie. Go to the options menu, Network preferences, Protocols, and select "Show Alert before Accepting a Cookie". You can also look at the cookie file on your hard disk with a text editor. If interested in seeing the cookies on your hard disk, search for a text file called cookies.txt. If you're using Windows 95, you can locate it with the Start-Find-Files-cookies.txt.

Cracker A term coined by computer hackers, who felt they were getting too much bad press. A cracker is anyone who's proficient at cracking codes and passwords for unethical and illegal purposes. A hacker, on the other hand, is a very noble computer jock who enjoys cracking codes, passwords, and assorted computer enigmas without harming anyone.

CSMA/CD Carrier Sense Multiple Access with Collision Detection. This is the method used by Ethernet to manage network traffic. Here is the basic problem. Multiple access means any computer can try to communicate with the network at any time. This differs from a token-ring network where only the computer with the token can gain access. If many computers are trying to gain access, how do you control the traffic on a network? Ethernet solves the traffic problem using carrier sensing. When a computer wants to send data to a network, it first checks the network cable to see if another computer is sending data. If the line is busy, the computer waits a while and then tries again. When the line is clear, the computer can send its data. Here's a subtle point. Suppose two computers check the line at the same instant and find it clear. When they start sending data, the data of each gets corrupted because their bits overlap. The result is garbage. This is where collision detection comes in. After each computer sends its data, it checks to see if its data collided with another computer's data. If there was a collision, each computer will try to resend its data after a random interval. Since the interval is random, one of the colliding computers will get to the line first, and the other will have to wait until the line is clear.

Cyberspace The word "cyberspace" first appeared in a 1984 fantasy novel which described cyberspace as the world of computers and all those interesting people who are totally addicted to them. But now, it has a different meaning. Cyberspace refers to a new reality, the next level in the evolution of consciousness, the virtual world you are in when surfing the web.

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