[virtmach] instruction set

[Stephen Pelc]

> Dennis Yelle <dennis51@jps.net> writes:
> > Because this:
> >    if ( a < b )
> > is not the same as this:
> >    if ( (a-b) < 0 )
> 
> In what mathematics?
The results are the same for differences less than half the 
total range. If the difference on (say) a 16 bit system is 
greater than 2^15, then you need to consider the carry flag as 
well. Just comparing the sign of the result is called circular 
arithmetic, and it has its uses. However the results are not 
always what you would expect, as Dennis' example shows.

--
Stephen Pelc, sfp@mpeltd.demon.co.uk
MicroProcessor Engineering Ltd - More Real, Less Time
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