Calling nested COBOL programs

Use either CALL literal or CALL identifier statements to make calls to nested programs.

You can call a contained program only from its directly containing program unless you identify the contained program as COMMON in its PROGRAM-ID paragraph. In that case, you can call the common program from any program that is contained (directly or indirectly) in the same program as the common program. Only contained programs can be identified as COMMON. Recursive calls are not allowed.

Follow these guidelines when using nested program structures:

• Code an IDENTIFICATION DIVISION in each program. All other divisions are optional.
• Optionally make the name of each contained program unique. Although the names of contained programs are not required to be unique (as described in the related reference about scope of names), making the names unique could help make your application more maintainable. You can use any valid user-defined word or an alphanumeric literal as the name of a contained program.
• In the outermost program, code any CONFIGURATION SECTION entries that might be required. Contained programs cannot have a CONFIGURATION SECTION.
• Include each contained program in the containing program immediately before the END PROGRAM marker of the containing program.
• Use an END PROGRAM marker to terminate contained and containing programs.

You cannot use the THREAD option when compiling programs that contain nested programs.