Embedding instructive assertions in program design

Computer programs are operational schemes. Many programmers design, describe, and justify their programs while solely thinking " operationally". Yet, an operational perspective is insufficient. For many years, the important role of an assertional perspective is advocated. However, this perspective is debated [5]. Many are deterred from employing it, possibly because it is displayed with formal notations and mathematical logic. The objective of this paper is to offer the elaboration of this perspective through a natural, informal embedment of assertions in the design process. The essential, revealing, and instructive role of informal, yet concise and accurate assertions is motivated and elaborated; first through three stimulating illustrations, and then with a general instructional approach.