Time Sharing Options Extensions (TSO/E) is a licensed program that is based on Time Sharing Option (TSO). With TSO/E, users can interactively share computer time and resources. They can also enter the shell environment by logging on to a TSO/E session and entering the OMVS command. Other TSO/E commands logically mount and unmount file systems, create directories in a file system, and copy files to and from MVS™ data sets. Users can switch from the shell to their TSO/E session, enter commands or do editing, and switch back to the shell. For information about how to perform these tasks using TSO/E commands, see z/OS UNIX System Services User's Guide.