8.1. Overview of functions in SAA

The functionality of the interface is divided into some main
areas:

·    Subcommand handlers
     which trap and handle a command to an  external environment.
·    External function handlers
     extend the REXX language with external functions
·    Interpreting
     REXX scripts, either from a disk  file, or from memory.
·    Variable interface
     which makes it possible to access the variables in the
     interpreter, and allows operations like setting, fetching and
     dropping variables.
·    System exits
     which are used to hook into certain key points in the
     interpreter while it executes a script.

In the following sections each of these areas are described in
detail, and a number of brief but complete examples are given at
the end of the chapter.

The description is of a highly technical nature, since it is
assumed that the reader will be an application programmer seeking
information about the interface. Therefore, much of the content is
given as prototypes and C style datatype definitions. Although
this format is cryptic for non-C programmers, it will convey
exact, compact, and complete information to the intended readers.
Also, the problems with
ambiguity and incompleteness that often accompany a descriptive
prose text are avoided.


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