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From: tmoran@acm.org
Newsgroups: comp.lang.ada
Subject: Re: Calculate and set Parity
References: <3d879cde.85767138@news.cis.dfn.de>
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Xref: archiver1.google.com comp.lang.ada:29097
Date: 2002-09-18T00:17:15+00:00
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The XOR of the parities equals the parity of the XORed bytes.
Thus the code can be shortened:

>  MOV AL, DataLo  ; load a byte
>  AND AL, AL      ; set PF
  change AND above to XOR AL,DataHi
>  LAHF            ; load flags byte
>  SHR AH, 2       ; shift PF into bit 0
>  AND AH, 1       ; mask off all other bits
>  MOV DL, AH      ; result into DL
  drop the following lines
>  MOV AL, DataHi
>  AND AL, AL
>  LAHF
>  SHR AH, 2
>  AND AH, 1
>  XOR DL, AH      ; parities must be XORed to get cumulative result