The Terminal application lets you control the UNIX operating system under Mac OS X using a command-line interface or “shell”. In each Terminal window, a shell takes your keyboard input and executes the commands.
Mac OS X includes these shells: bash (the default shell), csh (tcsh), zsh, and ksh. You can install and use different shells if you wish.
You can use a different shell in each window or tab. You can specify a default shell to use in Terminal preferences. In a networked environment a system administrator can specify the default shell.
Choose Terminal > Preferences and click Startup.
Select “command (complete path)” and enter the path to the shell you want to use.
For more information about the features of the shells, enter “man” and the name of the shell.