INT 13h,  05h (5)        Format Cylinder                                  all

    Initializes each sector on a specified cylinder with sector address
    and size information.

       On entry:      AH         05h
                      AL         Number of sectors to format (diskette) or
                                 Interleave (XT)
                      CH         Cylinder number (10-bit value; upper 2 bits
                                 in CL)
                      DH         Head number
                      DL         Drive number
                      ES:BX      Pointer to address field list (See below)

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

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       Notes:         Values in DL less than 80h specify floppy disks;
                      values from 80h to 87h specify fixed disks.

                      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.

                      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. Also diskette operations that require
                      the diskette motor to be on will call INT 15h,
                      Service 90 (Device Busy), with the type equal to
                      "Diskette Drive Motor Start" (Type = FDh). This
                      allows the system to perform another task while the
                      drive motor is waiting to get up to speed.

       Interleave:    "Interleaving" is the process of putting logically
                      contiguous sectors in physically noncontiguous
                      locations, in order to to increase disk performance.
                      Below is outlined the different ways of changing the
                      interleave factor depending on the type of media
                      (fixed disk or diskette) and the machine type.

                      The pointer to the address field list (ES:BX) varies
                      depending on what type of machine and type of disk
                      (fixed or diskette) the formatting process will
                      occur on. Also the interleave factor is specified
                      differently for the different machines and disk
                      types. Below are the formats for the different types
                      of machines and disks.

       Diskette:      ES:BX points to a list of address marks for each
                      sector on the track to be formatted. Each address
                      mark consists of 4 bytes. Therefore, to format a 9-
                      sector track, the list MUST consist of 36 bytes (4 *
                      9). The 4 bytes making up the address mark are
                      defined as follows:

                          Byte 1 - Cylinder number (C)
                          Byte 2 - Head number (H)
                          Byte 3 - Sector number (R), or Record number
                          Byte 4 - Sector Size (N)
                                      0 - 128 bytes per sector
                                      1 - 256 bytes per sector
                                      2 - 512 bytes per sector
                                      3 - 1024 bytes per sector

                      Note that you can change the interleave factor by
                      specifying byte 3 (sector number) in a non-
                      sequential order.

                      Standard MS-DOS diskettes are formatted with 512
                      bytes per sector (N=2) and with no interleave. Thus,
                      the address field list for a standard MS-DOS nine-
                      sector track would look like this:

                             C H R N    C H R N    C H R N ... C H R N
                             0 1 1 2    0 1 2 2    0 1 3 2     0 1 9 2

                      Before formatting a diskette, if there is more than
                      one type of diskette supported by the drive, you
                      will need to call Service 17h (Set DASD Type for
                      Format) or Service 18h (Set Media Type for Format).
                      If these services are not called, Service 05h will
                      format the disk using the maximum disk type
                      supported by the disk drive. Older machines that
                      don't support Service 17h (Set DASD Type for Format)
                      or Service 18h (Set Media Type for Format) may have
                      to directly modify the Diskette Drive Parameter
                      Table. This table is pointed to by INT 1Eh. If
                      modifications are made to the Diskette Parameter
                      Table, make sure the original values are restored.

       XT             The XT uses the AL register to specify the
                      interleave factor. The pointer ES:BX is not needed
                      for the XT.

       AT and XT-286  These machines use an address table (pointed to by
                      ES:BX), similar to the one used in diskette mode but
                      with a slight variation. The buffer must be 512
                      bytes long. The first 2 * (sectors per track) bytes
                      contain information for each sector on the track.
                      For each sector, there are 2 bytes in the table.
                      These 2 bytes are defined as follows:

                            Byte 1 - Sector Format state (F)
                                      00h - Good sector
                                      80h - Bad sector
                            Byte 2 - Sector number (N)

                      For example, the following table is used to format a
                      track for a fixed disk with 17 sectors per track and
                      an interleave factor of 3.

           db    00h, 01h, 00h, 07h, 00h, 0Dh, 00h, 02h, 00h, 08h, 00h, 0Eh
           db    00h, 03h, 00h, 09h, 00h, 0Fh, 00h, 04h, 00h, 0Ah, 00h, 10h
           db    00h, 05h, 00h, 0Bh, 00h, 11h, 00h, 06h, 00h, 0Ch