From Goto-Less to Structured Programming: the Legacy of Edsger W

memorial Senior Lead Editor: Dale Strok software@computer.org

From Goto-less to Structured Programming: The Legacy of Edsger W. Dijkstra

Peter P. Chen

id you know that Edsger I am a “programmer!” In 1972, Dijkstra published “Notes Dijkstra just passed away?” The first time I saw Dijkstra was on Structured Programming” (Struc- When I first heard the news, I when he delivered his Turing Award tured Programming, O.J. Dahl, E.W. was shocked. “How could acceptance speech. I was one of the Dijkstra, and C.A. Hoare, eds., Acad- this happen?!” I asked my- many people who stood for an hour emic Press, 1972). This triggered the D self. Last year (but it seemed to listen to that speech because all the Structured Programming movement, just yesterday) when Edsger and I sat seats were filled. It was worth it: he which helped many of us improve our together on a small bus leaving told us a story I will never forget. practices. the Software Pioneers Conference in When he applied for a wedding li- A survey of more than 1,000 col- downtown Bonn, Germany, to return cense in 1957, Dutch law required him lege professors identified the 38 most to our hilltop hotel, he looked to declare his profession. Filling in the influential papers in computer science healthy. On that bus ride, we dis- form, Dijkstra stated he was a “pro- (Great Papers in Computer Science, P. cussed the interesting difficulties he grammer.” The Amsterdam authorities Laplante, ed., West Publishing Co., 1996; had faced early on in his career. Al- claimed there was no such profession www.csc.lsu.edu/~chen/greatpapers. though he had run into obstacles, he and rejected his initial application. As a htm), and Dijkstra authored five of could now laugh about them since he result, his marriage certificate stated his them. In June 2001, at the Software had discovered ways to overcome profession as “theoretical physicist.” Pioneers Conference, about 1,200 them and change history. Today as I What struck me 30 years ago and still software professionals saw Dijkstra recall his face and soft voice, I see the resonates in my mind today is how speak for the last time. Fortunately, smile of a man who revolutionized Dijkstra was proud to be a program- that speech is preserved in streaming software development. mer instead of a theoretical physicist. video (www.sdm.de/conf2001/index_ This is the kind of person software de- e.htm) and book/DVD (Software Pio- A short biography velopment needs; being proud of one’s neers: Contributions to Software Engi- Edsger W. Dijkstra was born in profession is one of the most crucial neering, M. Broy and E. Denert, eds., the Netherlands in 1930 and died 6 psychological steps toward better- Springer-Verlag, 2002) format. August 2002. After receiving his PhD quality work. in computing science from the Uni- dsger Dijkstra is one of the most in- versity of Amsterdam, he worked as Major contributions fluential figures in computer sci- a programmer at the Mathematical Dijkstra’s most famous paper is E ence. His teachings (www.cs.utexas. Centre in Amsterdam, a math profes- probably “Goto Statement Considered edu/users/EWD) will resonate through sor at Eindhoven University of Tech- Harmful” (Comm. ACM, Mar. 1968, the work of software developers for nology, a research fellow at the Bur- pp. 147–148), which brought consid- many years to come. roughs Corp., and the Schlumberger erable attention to the problem of Centennial Professor of Computer software developers’ careless usage of Science at the University of Texas at the Goto statement. As a result, pro- Peter P. Chen is the Foster Distinguished Professor at Austin. He received the ACM Turing grammers today use it more carefully Louisiana State University and the inventor of the Entity- Award in 1972. or not at all. Relationship model. Contact him at [email protected].