IBM Version 4 manual API Compatibility, Exit programs That are documented Systemin

API Compatibility

Chapter 1. Application Programming Interface—Overview

Application programming interfaces (APIs) that are used on AS/400 busine puting systems provide paths into system functions. APIs are intended enced application programmers who develop system-level applications and AS/400 applications.

In	the broadest sense,applicationAS/400programming					interfaces (APIs)	are
any	formal	interfaces		that	are intended to be used in the building
These interfaces			can	include such		functions as:
Ÿ	Control	language	(CL)	commands
Ÿ	High-level language			(HLL)	instructions
Ÿ	Machine	Interface		(MI)	instructions

ŸExit programs

ŸCallable Operating System/400 (OS/400) APIs, such as those discussed System API Reference, SC41-5801, and documentation for various licensed programs.

The	APIs discussed	in this book are those	callable and bindable OS/4
OS/400	exit programs	that are documentedSystemin	APIthe Reference.

Figure 1-1 on page 1-2 shows how APIs fit into the system structure.

API Compatibility

Original program model			(OPM) APIs and Integrated Language Environment		(IL
APIs must	be	compatible from		one release to the next. To ensure	thi
ibility,	at	least one	of the	following is true:

ŸAny additional parameters for existing OPM APIs are placed after parameters and are optional parameters. For example, the Move Progr Message (QMHMOVPM) API has a group of required parameters and two groups of optional parameters.

Note: ILE APIs cannot have additional parameters added to existing

Ÿ Any additional data structures are provided as a new format.

ŸAny new information for a data structure is added at the end o replaces a field currently defined as reserved.

It is	IBM's intention that the	APIs will	continue to work	as	they or
any existing applications that use the APIs will continue				to	work with
However,	significant architectural	changes	may necessitate	incompatible

Some API definitions (for example, the UNIX** type of API definition lished by industry standards organizations where the degree of comp determined by the organizations.

 Copyright IBM Corp. 1997 1-1