Editing Structured programming (section)

===Theoretical foundation===
The [[structured program theorem]] provides the theoretical basis of structured programming. It states that three ways of combining programs&mdash;sequencing, selection, and iteration&mdash;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 [[Edsger W. Dijkstra|Dijkstra]] cited this paper himself.{{sfn|Dijkstra|1968}} 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 [[Edsger W. Dijkstra|Dijkstra]], [[Robert W. Floyd]], [[Tony Hoare]], [[Ole-Johan Dahl]], and [[David Gries]].