SYSSIM A "simulator" for various operating systems; will provide a few laughs. If anyone wishes to contribute a simulator for other operating systems, or has improvements to the ones provided here, please get in contact with Dr. Walraven. In a more serious vein, the program is an example of good FORTRAN-77 programming style. It is the essence of a talk on that subject given by Dr. Walraven at the New Orleans DECUS Symposium.