Comment by kragen
6 days ago
"Command" is a better term for what we call "statements" in imperative programming languages. "Statement" in this context is an unfortunate historical term; except in Prolog, these "statements" don't have a truth-value, just an effect. (And in Prolog we call them "clauses" instead.)
True.
In many early computer programming documents the term "order" was used instead of "statement", where "order" was meant as a synonym for "command" and not as referring to the ordering of a sequence.
Occasionally, but much more often (as in Mauchly's cited paper) an "order" was a machine instruction, not a high-level language "statement".
Yes, but that is mostly because in the first few years (including by the time of Mauchly), there were no "high-level" programming languages, so the "orders" composing the text of a program corresponded to instructions directly executable by the machine.
I believe that the term "statement" has been imposed by the IBM publications about FORTRAN, starting in 1956.
Before the first public documents about IBM FORTRAN, the first internal document about FORTRAN, from 1954, had used the terms "formula" for anything that later would be called "executable statement", i.e. for many things that would not have been called formulas either before or after that, like IF-formulas, DO-formulas, GOTO-formulas and so on, and the document had used "sentence" for what later would be called "non-executable statements" (i.e. definitions or declarations).
Before FORTRAN (1951 to 1953), for his high-level programming language Heinz Rutishauser had used the term "Befehl", which means "command". (For what we name today "program", he had used the term "Rechenplan", which means "computation plan".)
8 replies →
Is it? "Statement", defined by the dictionary as "the expression of an idea or opinion through something other than words.", seems quite apt. Symbols may end up resembling words, which perhaps is your contention, but technically they are only symbols.
Best I can tell, all usable definitions surrounding "Command" seem to suggest an associated action, which isn't true of all statements in imperative programming.
> Best I can tell, all usable definitions surrounding "Command" seem to suggest an associated action, which isn't true of all statements in imperative programming.
The defining characteristic of a programming "statement" is that it can perform some action (even if not all of them do), whereas statements in the usual everyday sense are inert. So it's not a good term.
> The defining characteristic of a programming "statement" is that it can perform some action
Given a declaration "statement" such as:
What is the expected action? Memory allocation... I guess? Does any compiler implementation actually do that? I believe, in the age of type systems being all the rage, one would simply see that as a type constraint, not as a command to act upon.
Expressing an idea (the values used henceforth should be integers) seems more applicable, no?
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The requirement for a truth value is just from how math/logic uses the term.
Well, and linguistics. A "statement" in the grammatical sense is a sentence that is declarative in form (as opposed to, in English, interrogative, imperative, or exclamatory) and which thus ostensibly has a truth-value.