Non-structured programming

Non-structured programming is the historically earliest programming paradigm capable of creating Turing-complete algorithms.^{[ citation needed ]} It is often contrasted with the structured programming paradigm, in particular with the use of unstructured control flow using goto statements or equivalent. The distinction was particularly stressed by the publication of the influential Go To Statement Considered Harmful open letter in 1968 by Dutch computer scientist Edsger W. Dijkstra, ^[1] who coined the term structured programming.^{[ citation needed ]}

Unstructured programming has been heavily criticized for producing hardly readable ("spaghetti") code.^{[ by whom? ]}

There are both high- and low-level programming languages that use non-structured programming. Some languages commonly cited^{[ citation needed ]} as being non-structured include JOSS, FOCAL, TELCOMP, assembly languages, MS-DOS batch files, and early versions of BASIC, Fortran, COBOL, and MUMPS.

Features and typical concepts

Basic concepts

A program in a non-structured language uses unstructured jumps to labels or instruction addresses. The lines are usually numbered or may have labels: this allows the flow of execution to jump to any line in the program. This is in contrast to structured programming which uses sequential constructs of statements, selection (if/then/else) and repetition (while and for).

References

1. Dijkstra (1968).

Sources

• Dijkstra, Edsger W. (March 1968). "Letters to the editor: Go to statement considered harmful" (PDF). Communications of the ACM . 11 (3): 147–148. doi:10.1145/362929.362947. S2CID   17469809. The unbridled use of the go to statement has as an immediate consequence that it becomes terribly hard to find a meaningful set of coordinates in which to describe the process progress. ... The go to statement as it stands is just too primitive, it is too much an invitation to make a mess of one's program.

Further reading

• Cobb, Gary W. (1978). "A measurement of structure for unstructured programming languages". ACM SIGSOFT Software Engineering Notes. 3 (5): 140–147. doi: 10.1145/953579.811114 . ISSN   0163-5948.

External links

• BPStruct - A tool to structure concurrent systems (programs, process models)