Enterprise COBOL for z/OS, Version 4.2, Programming Guide

A COBOL program can nest, or contain, other COBOL programs.
The nested programs can themselves contain other programs.
A nested program can be directly or indirectly contained in a program.

There are four main advantages to nesting called programs:

• Nested programs provide a method for creating modular functions and maintaining structured programming techniques.
  They can be used analogously to perform procedures (using the PERFORM statement), but with more structured control flow and with the ability to protect local data items.
• Nested programs let you debug a program before including it in an application.
• Nested programs enable you to compile an application with a single invocation of the compiler.
• Calls to nested programs have the best performance of all the forms of COBOL CALL statements.

The following example describes a nested structure that has directly and indirectly contained programs:

Related tasks