8 Dec
2005
8 Dec
'05
6:07 p.m.
Subject: Re: Legacy apps in Windows/OS X was Re: Old MS-DOS & Win Software
From: "Dwight K. Elvey" <dwight.elvey at amd.com>
Date: Thu, 08 Dec 2005 16:17:10 -0800 (PST)
To: cctalk at classiccmp.org
Hi
I still don't fully understand the decimal fuctions
of the 4004. It has similar problems with addition and
subtraction. It, of course, doesn't have to deal with
a half carry, being only 4 bits.
Dwight
The 4004 is as they say a "whole nother animal". The decimal
arithmetic is actually familiar theme amoung the 4bit(datapath)
class of machines TMS1000, NEC uCOM4 and uCOM75, and others
dealing with decimal quantities is both easier (no conversions)
and allows the data areas in memory to be organized or thought
of as long registers of decimal digits. Of course the Carry
has to reflect numeric overflows greater than 9d instead of Fh.
Allison