A B S T R A C T
CU SIM is an interactive low-level computer simulation packa=e that runs on the Macintosh computer. Users of the package specify the details of the CPU to be simulated, including the registers, i/o channels, main memory, the microinstruction set, machine instructions, and assembly language instructions. Users can then create machine or assembly language programs using the built-in text editor and assembler and can run their programs in the simulator. It is possible to step through the execution of a program one machine instruction or microinstruction at a time and even to back up one instruction at a time. Also, users may choose to edit the contents of any c o m p o n e n t and then continue execution. The main window displays the state of the machine at every step.