REXX General Concepts

The REstructured eXtended eXecutor (REXX) language is particularly suitable for command procedures, application front ends, user-defined macros (such as editor subcommands), user-defined XEDIT subcommands, prototyping, and personal computing.

REXX is a general purpose programming language like PL/I. REXX has the usual structured-programming instructions such as IF, SELECT, DO WHILE, and LEAVE, and a number of useful built-in functions.

The language imposes no restrictions on program format. There can be more than one clause on a line, or a single clause can occupy more than one line. Indentation is allowed. You can, therefore, code programs in a format that emphasizes their structure, making them easier to read.

There is no limit to the length of the values of variables, as long as all variables fit into the storage available.

Implementation maximum: No single request for storage can exceed the fixed limit of 16MB. This limit applies to the size of a variable plus any control information. It also applies to buffers obtained to hold numeric results.

The limit on the length of symbols (variable names) is 250 characters.

You can use compound symbols to construct arrays and for other purposes, for example:

NAME.Y.Z

Y and Z can be the names of variables or can be constant symbols.

REXX programs can reside in REXX File System directories or in MVS partitioned data sets. REXX programs usually have a file type of EXEC.

A language processor (interpreter) runs REXX programs. That is, the program is processed line-by-line and word-by-word, without first being translated to another form (compiled). The advantage of this to the user is that if the program fails with a syntax error, the point of error is clearly indicated, which helps to understand the difficulty and correct it.