The Korn shell is the UNIX shell (command execution program, often called a command interpreter ) that was developed by David Korn of Bell Labs as a comprehensive combined version of other major UNIX shells. Incorporating all the features of C shell ( csh ) and Tab C-shell ( tcsh ) with the script language features similar to that of the Bourne shell , the Korn shell is considered the most efficient shell. Korn, Bourne, and C are the three most commonly used UNIX shells.
The Korn shell is considered a member of the Bourne shell family and uses as its shell prompt (character displayed to indicate readiness for user input) the $ symbol. Because it is the easiest shell to use, inexperienced users usually prefer the Korn shell and, not surprisingly, it is the one most often used in commercial environments.
Sometimes known by its program name ksh , the Korn is the default shell on many UNIX systems.