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Concept
DIGITAL Command Language
Summary
DIGITAL Command Language (DCL) is the standard command language adopted by many of the operating systems created by Digital Equipment Corporation. DCL had its roots in IAS, TOPS-20, and RT-11 and was implemented as a standard across most of Digital's operating systems, notably RSX-11 and RSTS/E, but took its most powerful form in VAX/VMS (later OpenVMS). DCL continues to be developed by VSI as part of OpenVMS.
Written when the programming language Fortran was in heavy use, DCL is a scripting language supporting several data types, including strings, integers, bit arrays, arrays and booleans, but not floating point numbers. Access to OpenVMS system services (kernel API) is through lexical functions, which perform the same as their compiled language counterparts and allow scripts to get information on system state. DCL includes IF-THEN-ELSE, access to all the Record Management Services (RMS) file types including stream, indexed, and sequential, but lacks a DO-WHILE or other looping construct, requiring users to make do with IF and GOTO-label statements instead.
DCL is available for other operating systems as well, including
VCL and VX/DCL for Unix,
VCL for MS-DOS, OS/2 and Windows,
PC-DCL and Open DCL for Windows/Linux
and Accelr8 DCL Lite for Windows.
DCL is the basis of the XLNT language, implemented on Windows by an interpreter-IDE-WSH engine combination with CGI capabilities distributed by Advanced System Concepts Inc. from 1997.
For the OpenVMS implementation, the command line parser is a runtime library () that can be compiled into user applications and therefore gives a consistent command line interface for both OS supplied commands and user written commands. The command line must start with a verb and is then followed by up to 8 parameters (arguments) and/or qualifiers (switches in Unix terminology) which begin with a '/' character. Unlike Unix (but similar to DOS), a space is not required before the '/'. Qualifiers can be position independent (occurring anywhere on the command line) or position dependent, in which case the qualifier affects the parameter it appears after.
Official source
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