A Spreadsheet Based Simulation Of Cpu Instruction Execution

Abstract

The Spreadsheet CPU simulates a central processing unit for teaching purposes. The simulator provides interactive instruction execution like the “Little Man Computer,” the LC-3, and other simulators, but it is not a stand-alone program. Instead, it is implemented atop an off-the-shelf copy of the Microsoft Excel spreadsheet. The spreadsheet cells make it easy for students to observe the simulator's internal operation and to modify its operation if necessary. The Spreadsheet CPU was originally used in introductory computer literacy classes to present the concept of the instruction cycle. Since then it has been used to study instruction set design in an undergraduate computer design class. The Spreadsheet CPU can present CPU design to a broader range of undergraduate students than conventional simulators. Unlike other approaches, the Spreadsheet CPU does not require a background in digital logic or associated design languages in order to modify the CPU's operation or to add or modify instructions. Students can observe all important intermediate results during the cycling of the Spreadsheet CPU, since these results appear in spreadsheet cells. This allows students to study CPU design and perform design experiments without prerequisites in digital design or even in binary arithmetic. The Spreadsheet CPU simulation is distributed with a Creative Commons license and is freely available for use and modification by interested instructors.