A hierarchy of control structures
Eberhard Wegner · ACM SIGPLAN Notices · 1973
Four classes of control structures for sequential programs are shown to offer increasir..rexpressive power .They allow control to be specified by (1) four well-chosen structures with one entry and one exit each ,(2) the one-entry loop with escapes , (3) the distributor-entered loop with escapes, an d (4) the unrestricted jump .It is shown that a given program scheme can be described by the one-entry loop wit h escapes if and only if all control paths from the start to a cycle enter that cycl e at the same node (irrespective of the number of nodes where the cycle is re-entered) .