Analysis of structured programs

We investigate various control structures to understand their computational complexity and limitations. It is generally felt that GOTO-less programs constructed from the classical primitives are very restrictive; structured programming languages like BLISS, however, incorporating Repeat-Exit constructs appear to ease this sense of restrictiveness. In this paper we analyze this construct. We answer a conjecture of Knuth and Floyd as a special case of the general theory. We also investigate a general Top-Down Programming construct, which we call the TDn-construct. We structurally characterize the class of GOTO-less programs. We also generalize such an analysis and solve an open problem of Böhm and Jacopini.