AbstractAn interactive assembly level debugging system has been developed to facilitate program development on an INTEL 8080A/8085 based microcomputer. It has features such as decoding machine level instructions into the assembly language, relocating programs in memory, changing instructions interactively at assembly level etc. This paper deals with the design of the assembly level debugging system and the various facilities and features it provides. The debugging system requires only 4.5K bytes of RAM besides the memory requirements of the application program that has to be debugged.