Use of computers have been traditionally in Management Information Systems (MIS) and Data Processing (DP). Recent advancements in networking, different needs of the users and improved techniques of software development have led to usage of computers in different ways. The most important new applications of computers are in the field of Decision Support Systems (DSS) and Office Automation Systems (OAS). Advancements in micro computers which can be effectively networked have helped to a great extent, popularity of DSS and OAS. In this paper, attempts are made to describe some of the important characteristics of DSS software. Based on the author's experience in developing a few real life DSS, distribution of the code in various modules of DSS have been described. Such an analysis should help the DSS developer in planning proper strategy for software development for DSS.