8 Dec
2005
8 Dec
'05
2:14 p.m.
Subject: Re: Legacy apps in Windows/OS X was Re: Old MS-DOS & Win Software
From: Jim Leonard <trixter at oldskool.org>
Date: Thu, 08 Dec 2005 15:55:58 -0600
To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Chuck Guzis wrote:
You lived a shelterd life.
8080/8085 have a flag that is set when ther eis a carry from the low 4
bits to the upper as part of the DAA (Decimal Adjust Accumulator). Not
only is it mostly undocumented therre are a bunch of instructions like
Jumps that work with it also undocumented. While I've never deleved
deeper than I had to with 8086/88 I'd bet it exits there and and with
a few more permutations added. It's not unique to Intel!
Allison
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?