The C shell is a Unix shell that was created by Bill Joy while he was a graduate student at University of California.
The C shell is a command processor typically run in a text window, allowing the user to type commands. The C shell can also read commands from a file, called a script. Like all Unix shells, it supports filename wildcarding, piping, here documents, command substitution, variables and control structures for condition-testing and iteration.
What differentiated the C shell from others, especially in the 1980s, were its interactive features and overall style. Its new features made it easier and faster to use. The overall style of the language looked more like C and was seen as more readable.
#!/bin/csh if ( $days > 365 ) then echo This is over a year. endif
Used wild cards
input and output redirection operations
A set of shell variables for customizing the shell environment
Alias for used commands