C shell is the UNIX shell (command execution program, often called a command interpreter ) created by Bill Joy at the University of California at Berkeley as an alternative to UNIX's original shell, the Bourne shell . These two UNIX shells, along with the Korn shell , are the three most commonly used shells. The C shell program name is csh , and the shell prompt (the character displayed to indicate readiness for user input) is the % symbol. The C shell was invented for programmers who prefer a syntax similar to that of the C programming language.
The other popular member of the C shell family is called tcsh (for Tab C shell) and is an extended version of C shell. Some of tcsh's added features are: enhanced history substitution (which allows you to reuse commands you have already typed), spelling correction, and word completion (which allows you to type the first couple of letters in a word and hit the tab key to have the program complete it).
Once considered " bug gy", the C shell has had a number of different versions developed to overcome the flaws in the original program. Most often, only experienced users prefer to use the C shell. C is frequently the default shell at universities and research organizations and is the default on many systems, especially those derived from Berkeley UNIX.