Nested Programs
A COBOL program may contain other COBOL programs. The contained (or nested) programs may themselves contain yet other programs. A contained program may be directly or indirectly contained within a program.
Figure 1 describes a program structure with directly and indirectly contained programs.
Figure 1. Nested Program Structure with Directly and Indirectly Contained Programs

The same user-defined word may be used in different programs to define different objects. In a particular program, a reference to an object always refers to the object defined in that program.