GDDM programming interface

GDDM V3R2 Base Application Programming Reference

GDDM programming interface

GDDM V3R2 Base Application Programming Reference
SC33-0868-02

This topic explains:

The external programming interfaces to GDDM that are available, and how to use them
The syntax conventions for coding GDDM calls
The types of data that are required for parameters in the calls
Programming-language-dependent considerations.

Access to the GDDM functions by the application program is by GDDM interface modules that are link-edited or loaded with the program. The interface modules convert call statements in the program to a standard internal interface to invoke the GDDM functions. This makes GDDM itself independent of the subsystem being used, and allows the use of three different application interfaces:

Nonreentrant interface

This is the standard interface for most application programs that use GDDM and do not require any special processing. Quasi-reentrancy (as defined by CICS) can be achieved using this interface.

Reentrant interface

This allows the programs using GDDM to be made reentrant with the advantages that reentrancy provides; that is, the ability of the program to be used by more than one user at the same time.

System programmer interface

This is provided for programmers who intend to use GDDM as the basis for a graphics system of their own. It enables GDDM functions to be written in a coded form, it gives greater control over the subsystem environment, and it allows more programming flexibility.

Notes:

1. An application program using the nonreentrant interface cannot use either of the other interfaces.

2. An application program can use the reentrant and system programmer interfaces interchangeably.

Subtopics:

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