The increased use of microcomputers in electoronic controllers for automobiles has caused an increase in control program design work. Such factors an pollution regulations have made more comprehensive control mechanism necessary, and attached greater importance to safety. These, in turn, have contributed to the program designer's work load.The Computer-Aided Program Analysis System (CAPAS) we developed analyzes instructions in a program designed in assembler, and presents them in an easy-to-understand form. Unlike a flowchart generator, CAPAS determines the branching conditions and data to be stored in memory, and generates flowcharts and their explanations. CAPAS enables designers with little experience to understand program functions. It also enables programs to be reused or developed by more than one designer without causing that part of the program for which a designer is not responsible to become a black box. CAPAS is expected to reduce debugging time and improve program quality.This report presents the basic principles of CAPAS and tells how it is applied to program module design.