Unix shell is command line interpreter. It processes one command or group of commands on command line when clicking Enter button.
There are several UNIX shell programs families. . The most important are the Bash shell, the Korn shell, and the TC shell. The shell families were developed for different purposes.

To create a UNIX script , use VI editor

Shell script begins with (#!) . #!/bin/ksh at the begining is used to invoke Korn Shell