Legacy apps in Windows/OS X was Re: Old MS-DOS & Win Software

Tony Duell ard at p850ug1.demon.co.uk
Thu Dec 8 16:11:20 CST 2005


> 
> Chuck Guzis wrote:
> > codes.  Inspection of the 808x instruction set can be very illuminiating,
> > particularly when it comes to arcana like which instructions modify (and
> > how) the half-carry flag, for example.
> 
> The "half-carry flag"?  Huh?

I believe it's a flag indicating a carry from the low nybble to the high 
nybble of the accumulator. That is, it indicates a carry out from the low 
half of the byte. 

It's mainly needed for BCD operations if memory serves.

-tony



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