Issuing commands and changing the environment are two important concepts in the Digital UNIX operating system.
Commands tell the operating system what to do.
The environment settings control how you will view the results. When you are logged in to Digital UNIX, you are working in a program called the shell. The shell accepts your commands at the shell prompt. The commands you type are then interpreted and carried out by the shell. The first word you type after the shell prompt should always be a Digital UNIX command.