IBM AS/400 manual Parameter-Passing Considerations, Program/Procedure Call Overview

Program/Procedure Call Overview

PGM X
PRC_A
PRC_B
PRC_C
PRC_A	Recursive Call

Call Stack (bottom entry is most recent)
Figure	60. Recursive Call Stack To Be Avoided
So while subprocedures can be called recursively, if you are not									a
recursion is occurring, you		may exhaust system resources.
	Attention!
Unconditional recursive calls can lead				to	infinite recursion			which	le
sive use of system resources. Infinite recursion can be								avoided
gramming. In general, a proper recursive procedure begins								with a t
determine if the desired result			has	been		obtained.	If	it has	b
the	recursive procedure	returns	to the		most	recent	caller.

Parameter-Passing Considerations

When	designing a call interface, you must make a number	of	decisions
how	parameters will be passed. On the other hand, if	you	are	the
most	of the decisions have already been made for you. The followin
the	parameter-passing considerations to keep in mind when	you	are	des
call	interface.

¹Compile-time parameter checking

The call interface of a prototyped call is checked at compile t ensures that:

– the data types are correctly used

– all required parameters are passed

– *OMIT is only passed where it is allowed.

¹Parameter passing method

Each HLL provides one or more ways of passing parameters. These m include: passing a pointer to the parameter value, passing a copy or passing the value itself.

¹ Passing operational descriptors

Chapter 10. Calling Programs and Procedures131