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   ◄Summary►  ◄Notes►  ◄Back►
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▀ All registers except the segment registers may be destroyed.
 
▀ When this function returns, the CPU flags originally pushed on the stack
  by the INT 25H instruction are still on the stack. The stack must be
  cleared by a POPF or ADD SP,2 to prevent uncontrolled stack growth and
  to make accessible any other values that were pushed on the stack before
  the call to INT 25H.
 
▀ Logical sector numbers are obtained by numbering each disk sector se-
  quentially from track 0, head 0, sector 1, and continuing until the last
  sector on the disk is counted. The head number is incremented before the
  track number. Logically adjacent sectors may not be physically adjacent,
  due to interleaving that occurs at the device-driver level for some disk
  types.
 
▀ The error code is interpreted as follows: The lower byte (AL) is the
  same error code that is returned in the lower byte of DI when an Int 24H
  is issued. The upper byte (AH) contains:
 
  80H  if attachment failed to respond
  40H  if seek operation failed
  20H  if controller failed
  10H  data error (bad CRC)
  08H  if direct memory access (DMA) failure
  04H  if requested sector not found
  02H  if bad address mark
  01H  if bad command
 
▀ [4.0+] When accessing partitions larger than 32 MB under MS-DOS version
  4, this function uses a parameter block with the following format:
 
  Bytes       Description
  ═══════     ═════════════════════════
  00H-03H     32-bit sector number
  04H-05H     number of sectors to read
  06H-07H     offset of buffer
  08H-09H     segment of buffer
                                    -♦-