Overview

THE DIGITAL COMMAND LANGUAGE, DCL, is the vehicle by which the interactive user communicates with the OpenVMS operating system. The user enters commands, which are analyzed and executed by the DCL command language interpreter to perform actions or display information. Commands can have dozens or hundreds of variations, many of which the user must understand intimately. A command language layer is present on all interactive operating systems, manifested as the Shell on Unix or REXX on IBM VM/SP. There are other command language interpreters for OpenVMS, including the Monitor Console Routine (MCR) command interpreter for PDP-11 RSX-11 compatibility, and the DEC/shell and the POSIX shell, both of which create an environment similar to the Unix command shell.

OpenVMS users soon find that they want to capture a series of DCL commands in a file so they can use the same series of commands quickly and accurately in the future. In this way, the file acts as a script, specifying actions to be taken automatically when the script is called up. Often the script can be significantly more useful if its commands can be varied from one use to the next. Therefore, most command languages inevitably evolve into programming languages. In the case of OpenVMS, DCL is the name given to both the interactive command language and the command programming language, which are really one and the same thing. A file containing a DCL program is called a command procedure.

The goal of this book is to help you...