Flow of control in the proof theory of structured programming

The proof theory of structured programming insofar as concerned with flow of control is investigated. Various proof rules for the while, repeat-until and simple iteration statements - all essentially variants of Hoare's original while rule - are analyzed with respect to their soundness and adequacy. Next, a recently proposed proof rule for recursive procedures due to Dijkstra is - after correction - shown to be a simple instance of Scott's induction rule. Finally, Manna & Pnueli's rule for total correctness of the while statement is formally justified using the Hitchcock & Park theory of program termination based on well-founded relations.