INT 25 for >32MB Partitions

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#1256

From: Forrest Gehrke,2C-119,7239,ATTBL
Date: Mon, 17 Jun 1991 16:41

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I am having difficulty trying successfully to code in
C an absolute disk read using the alternate (extended)
method for INT 25 required for reading into a disk
partition greater than 32MB.

Particularly, my problem is with the disk read packet
DS:BX which requires (and here I am quoting from
Ralf Brown's INT291 listing for this INT):

00h DWORD Sector Number
04h WORD Number of sectors to read
06h DWORD Transfer address

Sector number: is this the absolute sector number starting
from the partition sector, or is it the DOS boot sector?
If accessing the boot sector is this number 0?

Transfer Address: To where?  How is this address chosen?

If anyone has coded this successfully in C I would appreciate
receiving via email the code fragment involved.

Thanks,

--Forrest Gehrke feg@dodger.att.com

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!cis.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!att!cbnewsl!floyd!feg
From: feg@floyd.ATT.COM (Forrest Gehrke,2C-119,7239,ATTBL)
Newsgroups: comp.sys.ibm.pc.programmer,comp.os.msdos.programmer
Subject: INT 25 for >32MB Partitions
Keywords: C code ?
Message-ID: <1991Jun17.164151.2625@cbnewsl.att.com>
Date: 17 Jun 91 16:41:51 GMT
Sender: news@cbnewsl.att.com (NetNews Administrator)
Reply-To: feg@floyd.ATT.COM
Organization: AT&T Bell Laboratories
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