difference between c++; and ++c;

Mark M Mehl mehl at iastate.edu
Wed Apr 17 12:00:33 AEST 1991


>In article <1991Apr11.151933.25867 at ingres.Ingres.COM> mikes at ingres.com (Mike Schilling) writes:
>>We old folks use:
>>	c++;
>>	--c;

In <1991Apr12.100933.2854 at tkou02.enet.dec.com> diamond at jit345.swstokyo.dec.com (Norman Diamond) writes:
>Some of us older folks didn't want to bother learning PDP-11 machine language,
>and DIDN'T learn to do it that way!

Note that both the PDP-11 and Motorola 6809 processors do _not_ have
a pre-incrementing addressing mode or a post-decrementing addressing
mode; however, these processors do support post-inc and pre-dec
addressing modes.  As a result, it's _likely_ that:

c++ maybe much faster than ++c
and
--c maybe much faster than c--

for these two processors since they lack the required addressing
modes for the latter.  (Has anyone check this out?)

Since the modern CISC processor supports all possible permutations of
pre/post inc/decrementation addressing modes, I doubt there would be
much difference.  RISC processors (like the dual X,Y auto-indexing
performed by vector-orientated machines, e.g. DSP processors) maybe
a different story of course.

Followups back to comp.lang.c
-- 
 /\ Mark M Mehl, alias Superticker (Supertickler to some)
<><> Internet: mehl at IAstate.edu
 \/ Preferred UUCP: uunet!iastate.edu!mehl
Disclaimer: You got to be kidding; who would want to claim anything I said?



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