INT 13H 04H: Verify Sectors

                                                              [PC] [XT] [AT]
 Expects: AH    04H
          AL    sector count (see notes)
          CH    track (cylinder) number (0-n) ◄═╗
          CL    sector number (1-n) ◄═══════════╩══ (see notes)
          DL    drive: 0-3=diskette; 80H-81H=hard disk
          DH    head number
          ──────────────────────────────────────────────────────────────────
 Returns: AH    BIOS disk error code if CF is set to CY
          ──────────────────────────────────────────────────────────────────
    Info: This verifies that the CRC▲ was correct for the specified
          sector(s).  It does NOT actually compare disk data to memory.

   Notes: ■ CX is used as a 6-bit and 10-bit field to specify sector and
            cylinder.  See INT 13H 02H for details.

          ■ On diskette writes, this function stops a multi-sector
            operation at the last sector in a track.

          ■ On hard disks (with XT and AT BIOSes), a multi-sector operation
            continues on the next higher head of the same cylinder and if
            necessary, advances to the next higher cylinder on the first
            head.

          ■ Parameters are the same as for INT 13H 02H (read sectors).

See Also: DOS fn 440dH 62H (IOCTL verify track)
          INT 13H: BIOS Disk I/O
          ROM-BIOS Functions
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