The z/OS shell is modeled after the UNIX System V shell with some of the features found in the Korn shell. As implemented for z/OS UNIX System Services, this shell conforms to POSIX standard 1003.2, which has been adopted as ISO/IEC International Standard 9945-2: 1992.

The tcsh shell is an enhanced but compatible version of csh, the Berkeley UNIX C shell. It is a command language interpreter usable as a login shell and as a shell script command processor.

Figure 1 shows how these shells fit into z/OS®.

Figure 1. How the shells fit into z/OS