Chapter 6: The Digital Command Language

This chapter introduces the Digital Command Language (DCL) command line interpreter (CLI). For users who access OpenVMS through a terminal or terminal emulation program, DCL will be the primary interface to the system. Those users who have access to a GUI interface should also read this chapter; DCL commands and command procedures are an integral part of OpenVMS, even for GUI users.

Those readers with access to an OpenVMS system may find it helpful to try the examples presented throughout this book.

What is a CLI?

A CLI is a piece of software that accepts commands typed by a user at a terminal keyboard and causes them to be carried out. A program may have its own internal CLI, but the default CLI for commands typed at the OpenVMS system prompt is DCL.

When a command is entered, DCL determines whether it is a valid command. If it is not valid, DCL displays an appropriate error message and awaits further commands. On receiving a valid command, DCL determines which program, if any, should be executed to carry out the command. Most commands require the attention of a program, but some commands are carried out internally by DCL.

If a separate program must execute to carry out the command, DCL causes the program to run and supplies it with information from the command line. After the program has finished, DCL again takes over and awaits the next user command.

While waiting for you to enter a command, DCL presents a prompt, a signal that it is waiting for your input. By default, that prompt is a single dollar sign ($). ^[1]

^[1]DCL, unlike a UNIX system's CLI, does not present a different prompt when the user has root access. The concept of root access has no exact equivalent in OpenVMS.