z/OS® is ideal for processing batch jobs– workloads that run in the background with little or no human interaction. However, z/OS is just as much an interactive operating system as it is a batch processing system. By interactive we mean that end users (sometimes tens of thousands of them concurrently) can use the system through direct interaction, such as commands and menu style user interfaces.

In z/OS, the facility known as Time Sharing Option/Extensions or TSO allows multiple users to log on and interactively share the resources of the mainframe. TSO also provides users with a limited set of basic commands; using this set is sometimes called using TSO in its native mode.

ISPF is a menu-driven interface for user interaction with a z/OS system. The ISPF environment is executed from native TSO. ISPF provides utilities, an editor and ISPF applications to the user. To the extent permitted by various security controls, an ISPF user has full access to most z/OS system functions.

TSO/ISPF serves as both a system management interface and a development interface for traditional z/OS programming.

The z/OS UNIX® shell and utilities provide a command interface to the z/OS UNIX environment. You can access the shell either by logging on to TSO/E or by using the remote login facilities of TCP/IP (rlogin).

If you use TSO/E, a command called OMVS creates a shell for you. You can work in the shell environment until exiting or temporarily switching back to the TSO/E environment.