Topic summary
CHS conversion
Extracted from the Wikipedia article Logical block addressing.
CHS conversion
In the LBA addressing scheme, sectors are numbered as integer indexes; when mapped to CHS (cylinder-head-sector) tuples, LBA numbering starts with the first cylinder, first head, and track's first sector. Once the track is exhausted, numbering continues to the second head, while staying inside the first cylinder. Once all heads inside the first cylinder are exhausted, numbering continues from the second cylinder, etc. Thus, the lower the LBA value is, the closer the physical sector is to the hard drive's first (that is, outermost) cylinder.