INT 13h,  0Ch (12)       Seek to Cylinder                          fixed disk

    Positions the read/write heads over a specified cylinder for a fixed
    disk. This service can be performed on fixed disks only.

       On entry:      AH         0Ch
                      CH         Cylinder number (10-bit value; upper 2 bits
                                 in CL)
                      DH         Head number
                      DL         Drive number (Bit 7 must be set)

       Returns:       AH         Status of operation (See Service 01h)
                      CF         Set if error, else cleared
  --------------------------------------------------------------------------

       Notes:         The cylinder number is a ten-bit quantity (0 through
                      1023). Its most significant two bits are in bits 7
                      and 6 of CL; the remaining eight bits are in CH. The
                      starting sector number fits in the low-order portion
                      (lower 6 bits) of CL.

                      If an error is encountered, use Service 0h to reset
                      the drive and retry the operation.

                      Even though the head value is not needed, you must
                      supply a legal value--or else the seek will not be
                      performed and an error will be returned.

                      For the AT, XT-286, and PC Convertible, the BIOS
                      executes INT 15h, Service 90h (Device Busy), for the
                      diskette (Type = 01h) and the fixed disk (Type =
                      00h) prior to waiting for the interrupt. INT 15h,
                      Service 91h (Interrupt Complete), is executed upon
                      completion.