Microsoft KB Archive/97819

= Ambiguous References to Sector One and Sector Zero =

Article ID: 97819

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.1
 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Server 3.5

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This article was previously published under Q97819



This article discusses some inconsistencies in sector numbering.

Sector counting starts at 1 when referring to the physical disk geometry. The first sector is reference by head 0, cylinder 0, sector 1. When people refer to absolute sectors on a physical volume, however, they typically refer to sector 0 as the first sector. Many applications (for example, Norton Disk Doctor) refer to the first sector as sector 0. Other tools use different conventions.

Documentation often references sector 0, as it is less ambiguous than using sector 1. Sector 0 is clearly the first sector, even if you disagree with the convention. Sector 1 is the first sector to some people, and the second sector to others.

On a disk with 37 sectors per track, 8 heads, and 512 cylinders, Windows NT would look at the numbering as follows:

                                     absolute cylinder    head      sector       sector address   0          0           1              0 0         0           2              1   0          0           3              2   0          0           4              3

  0          0          36             35 0         0          37             36   0          1           1             37   0          1           2             38

  0          1          36             72 0         1          37             73   0          2           1             74   0          2           2             75

  0          7          36            294 0         7          37            295   1          0           1            296   1          0           2            297

511 7 36 151550 511 7 37 151551

Additional query words: prodnt sector zero one 0 1 one-based 1-based zero- based 0-based

Keywords: kbother KB97819

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