This note discusses a conceptual framework for Decision Support Systems. It traces the evolution of DSS based on two disparate approaches to management decisions that can be labelled as the Management Science Approach and the Behavioural Sciences approach. The note also discusses the basic characteristics of Decision Support System and how they differ from other computer based systems. A recent survey of DSS applications published in the literature till 1988 provides classification of the applications into various management disciplines. From this Technical Note the reader should be able to understand the specific features of DSS and the various considerations in the design of Decision Support System.