MIPSpro Power Fortran 90 is a Fortran 90 compiler that enables you to run Fortran 90 programs efficiently on Silicon Graphics multiprocessor systems, including CHALLENGE, Onyx, POWER CHALLENGE, and POWER Onyx. Power Fortran 90 analyzes a program, identifies loops that are safe to execute concurrently on parallel CPUs, and generates a parallel version of the program automatically. The Fortran 90 manual, MIPSpro Fortran 90 Programmer's Guide, describes the special driver options and source directives you can use to explicitly control parallel execution, and the environment variables used to regulate parallel execution at run time. This Guide documents the driver options and source directives used to achieve automatic parallelization of an unmodified Fortran 90 program.