INT 13h,  18h (24)       Set Media Type for Format                       many

    This service returns a Diskette Drive Parameter Table (DDPT) for a
    specified diskette drive. This service can be performed on diskettes
    only.

       On entry:      AH         18h
                      CH         Number of tracks (10-bit value; upper 2 bits
                                 in CL)
                      CL         Sectors per track
                      DL         Drive number (Bit 7 must be clear)

       Returns:       CF         Set if error, else cleared
                      AH         Status of operation (See Service 01h)
                      ES:DI      Pointer to 11-byte Diskette Drive Parameter
                                 Table.
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       Notes:         This service is not available for PCs, PCjrs, XTs
                      dated before 1/10/86, and ATs dated before 11/15/85.

                      Machines that support this service call it before
                      calling Service 05h (Format a Track).

                      For each supported media type, there is one Diskette
                      Drive Parameter Table (DDPT).

                      In the event that the Change Status line is active
                      (i.e., that a disk change has occurred), this
                      service first attempts to deactivate the Change
                      Status line (by properly recognizing the new
                      diskette). If unable to do so, the service returns
                      an error. Therefore, if no diskette is present in
                      the drive, 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) prior to waiting for the
                      interrupt. INT 15h, Service 91h (Interrupt
                      Complete), is executed upon completion. 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.