The principal postulates were used as guidelines in … [PL360] language: (1) Statements which express operations on data must correspond … (2) No storage element [c.f. registers] should be hidden … (3) The control of sequencing should be expressible … [e.g., conditional clauses] … [p. 60] the programmer should express explicitly which parts … [in order to minimize the number of expensive, cross references between segments].
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