Using Global Variables › Global Variable Basics and OPS/REXX

Global Variable Basics and OPS/REXX

This section describes global variables in the context of OPS/REXX.

At the basic level, a global variable is an OPS/REXX compound symbol that has a unique stem. For example:

GLOBAL.xyz

OPS/REXX Compound Symbol

Compound symbols let you establish an accurate and efficient way to address values. By design, they help you implement tables or arrays.

An OPS/REXX compound symbol is a named object that which you can assign a value or data. It is a powerful kind of variable because one or more variables can be included in the name of the compound symbol itself. In other words, what makes a compound symbol unique is that a portion of the name of the compound symbol itself can be a variable.

Typically, the name of the most simple type of a variable is an identifiable constant; most likely a character string.

On the other hand, consider a variable that is a compound symbol:

• The variable can have one or more fields of assignable, variable data in its name.
• The variable is identified first by the constant string portion of its name, the stem, and subsequently identified by the variable portion of its name, the tail.

Example: Compound Symbols

An analogy is the address system of a city. In this analogy, assume the following information:

• A one dimensional, simple variable, which has only a constant string for a name, is like an address that consists only of a street name.
• A two-dimensional compound symbol, one that has a constant stem and a variable as part of the name, is like an address that includes both a street name and a number.

For more information about compound symbols, see THE REXX LANGUAGE: A Practical Approach to Programming by M.F. Cowlishaw (Prentice Hall, 1990).