29 Jul
2005
29 Jul
'05
12:22 a.m.
Paul Koning wrote:
Actually, carry is easy. There's a simple trick I
learned on the
Alpha, but it applies anywhere.
Given UNSIGNED variables:
c = a + b;
if (c < a)
{ /* you got a carry */ }
Jerome Fine replies:
Fortunately on the PDP-11, the carry is automatic
in assembler, just "ADC" to the next word to be
included in the sum before adding the next pair of
words. Likewise for subtraction.
Multiplication and addition are a bit more complicated,
of course.
Sincerely yours,
Jerome Fine
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