Harddisk CHS to byte

From: Misha Alex (misha_zant@hotmail.com)
Date: Fri Aug 16 2002 - 03:46:36 EST


>>Hi,
> 1)How do convert C,H,S into bytes.
> How can one read in linux if we know the C,H,S.
>
> Also i tried the linear addressing linear = c*H*S + h*S +s -1 .But
>linear or linear*512 never gave me the exact byte offset to seek.
>
>I am working in linux and using a hexeditor to seek .How many exact bytes
>should i seek to find out the extended partition.I read the MBR and found
>the exteneded partiton.
>00 01 01 00 02 fe 3f 01 3f 00 00 00 43 7d 00 00
>80 00 01 02 0b fe bf 7e 82 7d 00 00 3d 26 9c 00
>00 00 81 7f 0f fe ff ff bf a3 9c 00 f1 49 c3 01
>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>
>
>See the third column it is 0f(extended windows).The cylinder is 639(7f81 h)
>and sector is 1 .I don't know where to exactly read for the next partiton.
>The byte offset for finding out the next partitions.
>
>If i open hda3(Mind you hda3 is an extended partition on hda) with a
>hexeditor i get
>
>00 01 81 7f 83 fe ff 7d 3f 00 00 00 00 82 3e 00
>00 00 c1 7e 05 fe ff ff 3f 82 3e 00 7e 04 7d 00
>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>
>.Now the first partition is of type 83 which is linux and the next
>extended partition is of type 05(extended) and cylinder894 and sec1.
>
>
>
>*************************************
>How do i find the next chain of extended partitions.I mean how do i convert
>cylinder 894 ,sec1 and head 0 into absolute bytes so that i can hexdump the
>next partition table for finding out ?
>************************************
>
>Thank you,
>Misha
>

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