Page "Structured programming" Paragraph 9

The structured program theorem provides the theoretical basis of structured programming.

It states that three ways of combining programs — sequencing, selection, and iteration — are sufficient to express any computable function.

This observation did not originate with the structured programming movement ; these structures are sufficient to describe the instruction cycle of a central processing unit, as well as the operation of a Turing machine.

Therefore a processor is always executing a " structured program " in this sense, even if the instructions it reads from memory are not part of a structured program.

However, authors usually credit the result to a 1966 paper by Böhm and Jacopini, possibly because Dijkstra cited this paper himself.

The structured program theorem does not address how to write and analyze a usefully structured program.

These issues were addressed during the late 1960s and early 1970s, with major contributions by Dijkstra, Robert W. Floyd, Tony Hoare, and David Gries.