www.americanscientist.org | American Scientist (linkrot)
...structured programming, a reform movement whose manifesto was Edsger W. Dijkstra's brief letter to the editor titled "Go to statement considered harmful." Structured programs were to be built out of subunits that have a single entrance point and a single exit (eschewing the goto command, which allows jumps into or out of the middle of a routine). Three such constructs were recommended: sequencing (do A, then B, then C), alternation (either do A or do B) and iteration (repeat A until some condition is satisfied). Corrado Böhm and Giuseppe Jacopini proved that these three idioms are sufficient to express essentially all programs.