1. In a computer system which creates executable programs from a plurality of compiled object modules, said plurality of object modules having at least one public and external reference and selected ones of the object modules of which are stored in at least one library file, an improved method for linking the object modules into an executable program, the improvement comprising: (a) providing each library file with a Standard Dictionary, said Standard Dictionary being a portion of each library file having entries which lists all public references from the object modules stored in the library file where a public reference is capable of satisfying an external reference in another object module; (b) providing each library file with an Extended Dictionary, said Extended Dictionary being a portion of each library file which has a dependent modules list for each object module in the library file; (c) for each public reference entry in the Standard Dictionary which is not an object module name, storing a reference to a name of an object module which includes the public reference; (d) for each public reference entry in the Standard Dictionary which is an object module name, storing a reference to the dependent object modules list in the Extended Dictionary for the named object module; (e) for each external reference in a non-library object module which is not satisfied by another non-library object module during linking, said computer system locating a public reference in said at least one library file which satisfies the external reference; and (f) said computer system determining from said Standard Dictionary and said Extended Dictionary which object modules from the library file are necessary for linking.