You can use the portability library libifport.a in one of two ways:
Add the statement USE IFPORT to your program. This statement includes the portability library libifport.a.
Call portability routines using the correct parameters and return value.
libifport.a is passed to the linker by default during linking. To prevent libifport.a from being passed to the linker, specify the -fpscomp nolibs option.
Using the libifport.a portability library provides interface blocks and parameter definitions for the routines, as well as compiler verification of calls.
Some routines in this library can be called with different sets of arguments, and sometimes even as a function instead of a subroutine. In these cases, the arguments and calling mechanism determine the meaning of the routine. The libifport.a portability library contains generic interface blocks that give procedure definitions for these routines.
Fortran 95/90 contains intrinsic procedures for many of the portability functions. The portability routines are extensions to the Fortran 95 standard. When writing new code, use Fortran 95/90 intrinsic procedures whenever possible (for portability and performance reasons).