Unlike OPM programs, ILE programs are not limited to using program calls. ILE programs can also use static procedure calls or procedure pointer calls to call other procedures. Procedure calls are also referred to as bound calls.
A static procedure call is a call to an ILE procedure where the name of the procedure is resolved to an address during binding — hence, the term static. As a result, run-time performance using static procedure calls is faster than run-time performance using program calls. Static calls allow operational descriptors, omitted parameters, and they extend the limit (to 399) on the number of parameters that are passed.
Procedure pointer calls provide a way to call a procedure dynamically. For example, you can pass a procedure pointer as a parameter to another procedure which would then run the procedure that is specified in the passed parameter. You can also manipulate arrays of procedure names or addresses to dynamically route a procedure call to different procedures. If the called procedure is in the same activation group, the cost of a procedure pointer call is almost identical to the cost of a static procedure call.
Using either type of procedure call, you can call:
Any procedure that can be called by using a static procedure call can also be called through a procedure pointer.
For a list of examples using static procedure calls, see Examples of Free-Form Call and Examples of CALL and CALLB. For examples of using procedure pointers, see the section on the procedure pointer data type in IBM Rational Development Studio for i: ILE RPG Reference.
You use the CALLP or both the CALLB and PARM operations to make a procedure call. You can also call a prototyped procedure with an expression if the procedure returns a value. If you use the CALLB and PARM operations, then the compiler cannot perform type checking on the parameters, which may result in run-time errors.