Because the macro facility
performs its tasks before SAS programs execute, the information that
the macro facility supplies does not depend on values that are accessed
or computed during the execution of a SAS program. However, sometimes
it is necessary to access or create macro variables during the execution
of a SAS program. There are several methods that enable the macro
facility to create or access macro variables at execution time. In
this chapter, you learn to use macro variables during execution of
the following: