C

C

Programming language in which much of the Linux kernel is written, as were later versions of Unix before it. C was created by some of the same people who created Unix, and its development mirrors that of Unix.

C++

Object-oriented programming language; originally designed to be an enhancement to C, but now seen as a popular alternative.

C#

Modern programming language, which uses similar syntax to C, created by Microsoft and re-created on Linux via the Mono project.

character device

How Linux refers to a device that sends/receives data asynchronously. For various technical reasons, this typically refers to the terminal display. See also block device.

checksum

Mathematical process that can be applied to a file or other data to create a unique number relative to the contents of that file. If the file is modified, the checksum will change, usually indicating that the file in question has failed to download correctly or has been modified in some way. The most common type of checksum program used under Linux is md5sum.

client

Shorthand referring to a computer that connects to a server.

closed source

The reverse of Open Source in which the source code is not available for others to see, share, or modify. See also proprietary.

code

See source code.

command

Input typed at the shell that performs a specific task, usually related to administration of the system and/or the manipulation of files.

command-line prompt

See shell.

commodity

In the context of hardware, describes PC hardware usually based around Intel or AMD processors that can be bought off the shelf and used to create sophisticated computer systems (as opposed to buying specially designed hardware). One reason for Linux’s success is its ability to use commodity hardware.

community

The general term for the millions of Linux users worldwide, regardless of what they use Linux for or their individual backgrounds. By using Linux, you automatically become part of the community.

compile

The practice of creating a binary file from source code. Usually achieved using the ./configure, make, make install series of commands and scripts.

config file

Configuration file; any file that contains the list of settings for a program. Sometimes it’s necessary to edit config files by hand using programs like vi or emacs, but often the program itself will write its config file according to the settings you choose.

copyleft

The legal principle of protecting the right to share a creative work, such as a computer program, using a legally binding license. Copyleft also ensures future iterations of the work are covered in the same way.

cracker

Someone who breaks into computer systems to steal data or cause damage. The term is not necessarily linked to Linux or Unix but was created by the community to combat the widespread use of hacker in this sense. The word hacker has traditionally defined someone who merely administers, programs, and generally enjoys computers.

cron

Background service that schedules tasks to occur at certain times, specified in anything up to minute-by-minute resolution. It relies on the crontab file.

CUPS

Common Unix Printing System; set of programs that work in the background to handle printing under Unix and Linux.

curses

Library that lets software present a semigraphical interface at the shell, complete with menu systems and simple mouse control (if configured). The version of curses used under Linux and Unix is called ncurses.

CVS

Concurrent Versioning System; application that allows the latest version of software packages to be distributed over the Internet to developers and other interested parties.