Modifying and then validating a program with many
interacting modules, such as procedures, is an expensive 
and complex task.  Thus, a maintenance environment containing 
an efficient program representation and tools that access 
that representation to assist the user in understanding,
modifying, analyzing, testing and debugging a program is
needed.

This paper presents our unified interprocedural graph, UIG, 
that combines the features of existing program representations 
to permit access to information for maintenance tasks.
The main benefit of this approach is the reduction in
storage space for the individual representations since redundant 
information is eliminated.  Another important benefit is the 
savings in access time to the various graphs since all algorithms 
access the UIG.  A single program representation also assists
in program understanding since relationships among program elements 
are incorporated into one graph.