Decimal V Binary??

From: Tom Jennings <>
Date: Sun Oct 10 00:02:18 2004

On Sun, 10 Oct 2004, der Mouse wrote:

> >> I've always wondered what systems/processors (other than IBM
> >> mainframes) that had hardware decimal arithmetic support.
> The VAX has packed decimal arithmetic instructions. Depending on which
> VAX, they may be microcoded or they may just trap to the OS for
> "macrocoded" emulation (of course the OS may choose to error out
> instead of bothering).

The lowly 8080 had DAA, Decimal Adjust for Addition. If I recall,
it handled "carry" from bit5 (and Cy?) after adding a BCD pair
in A.

Man, I wrote a lot of 8080 code, so much I still remember
opcodes and could puzzle out binary 20 years later, but it's
possible I never once used DAA. Hell, I used MOV A, A even.

(An inline pseudo-disassembler; a config file could specify
the IO port a tape drive interface was located and the program
modified itself to change all the port numbers for IN and
OUT. IO instructions following MOV A, A were modified.)
Received on Sun Oct 10 2004 - 00:02:18 BST

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