A CPU simulator that can design instruction sets has been developed. This simulator can use a stack. By using the stack, subroutine calls can be realized. The simulator also allows students to design their own instruction sets. The simulator simulates assembler programs using the instruction sets designed by the students. In addition, the simulator displayed the memory status in colors, making program execution easy to understand. After the Excel file was used in a class, a questionnaire survey was conducted. According to the results of the questionnaire survey, almost all students felt that this Excel file was very useful to understand computer architecture.
