COBOL Manual for TNS/E Programs (H06.03+)

Program Compilation

HP COBOL Manual for TNS/E Programs—520347-003

11-4

Calling and Called Programs

Many languages have declarations that distinguish main programs from subprograms.

COBOL does not use the term “subprogram.” Instead, it defines a program as a

“calling program” if it contains a CALL or ENTER statement and defines a program as

a “called program” if it is the object of a CALL or ENTER statement. A program can be

both a calling program and a called program. The distinction is one of usage, not of

explicit declaration. In Example 11-1, A-PROGRAM is a calling program and A-

FRIEND is both a called program and a calling program.

If a called COBOL program is to receive parameters, it must have a Linkage Section

(see Linkage Section).

The statement a COBOL program uses to call another program depends on the

language in which the called program was written.

Called programs are not required to be in the main program’s compilation unit (see

Compilation Units).

How an HP COBOL Program Calls a Non-COBOL Program

Any HP COBOL program can call a non-COBOL program with the ENTER statement.

An HP COBOL program that was compiled with the PORT directive can also call a

non-COBOL program with the X/Open CALL statement. The difference between the

ENTER statement and the X/Open CALL statement is that the ENTER statement

attempts to coerce the actual parameters into the types of the formal parameters, while

the X/Open CALL statement reports an error if the types of the actual and formal

parameters do not match.

Just as HP COBOL object programs can be read from an object file and included in the

target file during the (optional) linking phase of ECOBOL compilation, object programs

from other languages can also.

Table 11-1. Statements for Calling Programs

Language of Called Program Statement for Calling Program

HP COBOL CALL

HP C ENTER or X/Open CALL

HP C++ ENTER or X/Open CALL

pTAL ENTER or X/Open CALL

Note. You cannot put any combination of TNS, TNS/R, or TNS/E object files into a single

object file.