A recursive routine is a routine that calls itself. Recursion is the most natural method of solving certain problems, such as:
Although you can write any recursive routine as a straight iterative routine, the use of a recursive routine can simplify the program's logic.
In this COBOL system, a program can be recursive provided it is not nested inside another program and it has a Local-Storage Section. A program can call itself via either its program-id or an entry point.
Each call of a recursive routine is called an instance. Each instance needs a different set of the data items used by the routine; so this COBOL system enables you to have a Local-Storage Section. A run-time error message is issued if you try to use recursion in a program that does not contain a Local-Storage Section.
See Related information for examples of recursion and recursive routines.
A more extensive illustration of recursive routines can be seen in the example program diophant.cbl. This program solves the linear equation Ax + By = 0 for integers x and y.
See Related information for the example program diophant.cbl.