Accessibility of Identifiers in a Module

Abstract

Traditionally, names in one Fortran program unit have been unknown in other program units, but, as discussed in Chapter 7, the module changes this. If no special action is taken, a module user has access to the names in the specification part of the module, where the specification part consists of the portion of the module remaining after any subprograms it contains (along with any CONTAINS statement that may be present) are removed. Also, a module user has access to the names of the procedures defined by module subprograms unless special action is taken. While the capability of sharing names in modules is a major improvement to the language, it also opens the door to the possibility of name clashes arising in ways not historically encountered by Fortran programmers. For example, when programmers are working in teams, software development may be slowed because module authors and module users have chosen names that conflict. Also, a programmer may wish to use a module in an existing program, where the module is supplied only in the form of object code by an outside organization, but accessible names in the module may duplicate names with different meanings already in the program.