Int 13h, 15h            Read DASD Type                                   many

    Returns the type of interface associated with a drive and also the
    number of sectors the drive contains. Can be used to determine if
    a diskette drive supports the sensing of a diskette change.

        Entry   AH = 15h
                DL = Drive number

        Return  CF Set if error, else cleared
                AH    = Disk type (see below)
                        Status of operation if error (see Service 01)
                CX:DX = If no error and AH <> 0, then 4-byte integer
                        with number of sectors.

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    This service is not available for PCs, PCjrs, and XTs dated before
    1/10/86.

    This service allows you to determine whether a drive supports the
    Change Line Status service (Service 16h). The Change Line Status
    informs the system whether or not a diskette has changed since the
    last access to it.

    Use Service 17h (Set DASD Type) to set the type.

                Disk Type
                AH      Meaning
                00h     Drive not present
                01h     Diskette, no change line available
                02h     Diskette, change line available
                03h     Fixed Disk

    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.