Terminals come with v arious memory amoun ts. This a￿ects the amoun t of information y ou can access at one time. When eac h line of the screen is ￿lled, the top line scrolls up to mak e room for a new line at the bottom. This con tinues until terminal memory is ￿lled. A t this point, information will be lost from view when y ou enter another line because the line scrolled up at the top of the memory bu￿er is no longer a vailable.

Giving Commands to MPE/iX

There are several ways to command MPE/iX: commands, command ￿les, and user-de￿ned commands (UDCs). These alternativ es are described in the subsections belo w and shown in Figure 1-4.

Figure 1-4. Commanding MPE/iX

MPE/iX Commands

MPE/iX commands perform man y di￿erent functions: managing ￿les, compiling programs, executing programs, and so on. Man y commands actually in voke subsystems, causing other programs to run. Some commands require that y ou have capabilities on the system bey ond that of the normal user. F or example, they ma y require Account Manager (AM), System Manager (SM), or System Supervisor (OP) capability .

In a session, the command in terpreter uses a leading colon (:) as a prompt c haracter to indicate that it is expecting y ou to enter an MPE/iX command. In jobs, y ou enter the leading colon before an MPE/iX command to iden tify it. In both cases, the system disregards blanks between the leading colon and the MPE/iX command.

1-16 OVERVIEW