From: nickroberts@blueyonder.co.uk (Nick Roberts)
Subject: Re: Calculate and set Parity
Date: Wed, 18 Sep 2002 20:25:53 GMT
Date: 2002-09-18T20:25:53+00:00 [thread overview]
Message-ID: <3d88df22.168279476@news.cis.dfn.de> (raw)
In-Reply-To: fCPh9.503263$UU1.83536@sccrnsc03
On Wed, 18 Sep 2002 00:17:15 GMT, tmoran@acm.org strongly typed:
>The XOR of the parities equals the parity of the XORed bytes.
>Thus the code can be shortened:
>...
Absolutely correct. I forgot this in my haste (and the lateness of the
hour). The revised code then is:
MOV AX, Data ; load a 16-bit word
XOR AL, AH ; XOR upper byte with lower
; and at the same time set PF
LAHF ; load flags byte
SHR AH, 2 ; shift PF into bit 0
AND AH, 1 ; mask off all other bits
which leaves the result in AH.
--
Nick Roberts
Per Ardua ad Disastra
next prev parent reply other threads:[~2002-09-18 20:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-16 16:42 Calculate and set Parity Sebastian
2002-09-16 18:14 ` Stephen Leake
2002-09-16 18:58 ` Jeffrey Carter
2002-09-16 19:51 ` tmoran
2002-09-17 1:36 ` tmoran
2002-09-17 22:05 ` Nick Roberts
2002-09-17 23:23 ` tmoran
2002-09-18 0:17 ` tmoran
2002-09-18 20:25 ` Nick Roberts [this message]
2002-09-18 2:52 ` SteveD
2002-09-18 18:29 ` Parity using 'Write, was " tmoran
2002-09-18 18:47 ` David C. Hoos
2002-09-18 22:17 ` tmoran
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox