In recent years the subject of computer programming has been recognized as a discipline whose mastery is fundamental and crucial to the success of
many engineering projects and which is amenable to scientific treatment and
presentation. It has advanced from a craft to an academic discipline. The
initial outstanding contributions toward. this development were made by
E. W. Dijkstra and C. A. R. Hoare. Dijkstra's "Notes on Structured Pro-
gramming"* opened a new view of programming as a scientific subject and
an intellectual challenge, and it coined the title for a "revolution" in pro-
gramming. Hoare's "Axiomatic Basis of Computer Programming"t showed
in a lucid manner that programs are amenable to an exacting analysis based
on mathematical reasoning. Both these papers argue convincingly that many
programming errors can be prevented by making programmers aware of the
methods and techniques which they hitherto applied intuitively and often
unconsciously. These papers focused their attention on the aspects of com-
position and analysis of programs, or, more explicitly, on the structure of
algorithms represented by program texts. Yet, it is abundantly clear that a
systematic and scientific approach to program construction primarily has a
bearing in the case of large, complex programs which involve complicated
sets of data. Hence, a methodology of programming is also bound to include
all aspects of data structuring. Programs, after all, are concrete formulations
of abstract algorithms based on particular representations and structures
of data.