Re: C ++ and -- (Richard A Hammond)
Fri, 22 Oct 1993 20:51:48 GMT

          From comp.compilers

Related articles
pointer elimination in C (Karen Miller) (1993-10-05)
Re: pointer elimination in C (Robin Popplestone) (1993-10-22)
Re: C ++ and -- (1993-10-22)
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Newsgroups: comp.compilers
From: (Richard A Hammond)
Keywords: C, history, design
Organization: Compilers Central
References: 93-10-032 93-10-096
Date: Fri, 22 Oct 1993 20:51:48 GMT

In an article in comp.compilers Robin Popplestone <> writes:
>C was, as they would say in Congress, -very unique- in providing pointer
>arithmetic. This simply reflected the fact that good compilers had to be
>shoehorned into a tiny computer, the DEC-11, and there was a simple
>one-to-one mapping between something like *x++ and one machine

Not exactly, to quote from Dennis Ritchie in the 2nd History of Programming
languages Conference, ACM SIGPLAN Notices, Vol 28, No. 3, March 1993, pg 203
    Thompson went a step further by inventing the ++ and -- operators, ...
    People often guess that they were created to use the auto-increment and
    auto-decrement address modes provided by the DEC PDP-11 on which C and Unix
    first became popular. This is historically impossible, since there was no
    PDP-11 when B was developed. ... a stronger motivation for the innovation
    was probably his observation that the translation of ++x was smaller than
    that for x = x + 1.

So it was shoehorning into a small computer, the PDP-7. It wasn't for
PDP-11 instructions.

Rich Hammond

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