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"all religions, arts and sciences are branches of the same tree. all these aspirations are directed toward ennobling man's life, lifting it from the sphere of mere physical existence and leading the individual towards freedom." albert einstein

Primeval C: two very early compilers

Dennis Ritchie, the creator of the C programming language and co-creator of UNIX operating system, had been curating some old DECtapes, and he offered some of the artifacts. Unfortunately existing tapes lack interesting things like earliest Unix OS source, but some indicative fossils have been prepared for exhibition.

"As described in the C History paper, 1972-73 were the truly formative years in the development of the C language: this is when the transition from typeless B to weakly typed C took place, mediated by the (Neanderthal?) NB language, of which no source seems to survive. It was also the period in which Unix was rewritten in C.

In looking over this material, I have mixed emotions; so much of this stuff is immature and not well-done, and there is an element of embarrassment about displaying it. But at the same time it does capture two moments in a period of creativeness and may have some historical interest.

Two tapes are present here; the first is labeled "last1120c", the second "prestruct-c". I know from distant memory what these names mean: the first is a saved copy of the compiler preserved just as we were abandoning the PDP-11/20, which did not have multiply or divide instructions, but instead a separate, optional unit that did these operations (and also shifts) by storing the operands into memory locations. [...]

"prestruct-c" is a copy of the compiler just before I started changing it to use structures itself.

It's a bit hard to get really accurate dates for these compilers, except that they are certainly 1972-73. There are date bits on the tape image, but they suffer from a possible off-by-a-year error because we changed epochs more than once during this era, and also because the files may have been copied or fiddled after they were the source for the compiler in contemporaneous use.

The earlier compiler does not know about structures at all: the string "struct" does not appear anywhere. The second tape has a compiler that does implement structures in a way that begins to approach their current meaning. Their declaration syntax seems to use () instead of {}, but . and -> for specifying members of a structure itself and members of a pointed-to structure are both there.

mortdeus, from Hacker News, has mirrored these files into a github repo where you can view these files.

Read more at Dennis Ritchie's original article.

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De: russell Fecha: 2018-05-17 13:20

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