Abstract: This paper is intended to show how PSL/PSA may be used to provide a computer aid design for information processing and software engineering methodologies and to briefly describe the history of the Software engineering development.Structured system life cycle methods have been described in a number of publications.This paper is based on a synthesis of these publications and introduces the Problem Statement Language(PSL)and the Problem Statement Analyzer(PSA).PSL/PSA is a computer-aided technique for structured documentation and analysis of the information processing system.It is also a important tool for the software engineering.