System operation control

This describes how you can control the operation of the system using control language (CL), menu options, and system messages.

• Control language
  Control language (CL) is the primary interface to the operating system. CL can be used at the same time by users at different workstations, in batch and interactive jobs and in CL programs and procedures.
• Menus
  The system provides a large number of menus that allow users to perform many system functions just by selecting menu options.
• Messages
  A message is a communication sent from one user, program, or procedure to another.