itly expressed his doubts whether the go to statement should be treated on equal syntactic footing with the assignment statement. To a modest extent I blame myself for not having then drawn the consequences of his remark.

The remark about the undesir-ability of the go to statement is far from new. I remember having read the explicit recommendation to restrict the use of the go to statement to alarm exits, but I have not been able to trace it; presumably, it has been made by C.A.R. Hoare. In [ 1, Sec. 3. 2. 1.] Wirth and Hoare together make a remark in the same direction in motivating the case construction: “Like the conditional, it mirrors the dynamic structure of a program more clearly than go to statements and switches, and it eliminates the need for introducing a large number of labels in the program.”

In [ 2] Guiseppe Jacopini seems to have proved the (logical) super-fluousness of the go to statement. The exercise to translate an arbitrary flow diagram more or less mechanically into a jumpless one, however, is not to be recommended. Then the resulting flow diagram cannot be expected to be more transparent than the original one.

REFERENCES

1. Wirth, Niklaus, and Hoare, C.A.R. A contribution to the development of ALGOL. Comm. ACM 9 (June 1966), 413–432.

2. Bohn, Corrado, and Jacopini, Guiseppe. Flow Diagrams, Turing machines and languages with only two formation rules. Comm. ACM 9 (May 1966) 366–371.

EDSGER W. DIJKSTRA Technological University Eindhoven, The Netherlands Communications of the ACM March 1968, Vol. 11, No. 3, pg 147

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