In COBOL, contained subprograms are not visible to other contained subprograms by default. You must use the IS COMMON PROGRAM clause to make a subprogram visible to other subprograms:

IDENTIFICATION DIVISION.
PROGRAM-ID. MAIN.
PROCEDURE DIVISION.
    ...
    EXIT PROGRAM.

IDENTIFICATION DIVISION.
PROGRAM-ID. A.
* CAN CALL B
    CALL B.
END-PROGRAM A.

IDENTIFICATION DIVISION.
PROGRAM-ID. B IS COMMON PROGRAM.
* CANNOT CALL A
    CALL A
END-PROGRAM B.
END-PROGRAM MAIN.

The Java programming language has data hiding, but it is used to restrict access to methods within a class from methods outside of the class. Class members labeled as public are visible to any method in any other class. Class members labeled as private are not visible to any method in any other class.