Int 13h, 10h            Test for Drive Ready                       fixed disk

    Tests to see if the fixed disk drive is ready. This service can be
    performed on fixed disks only.

        Entry   AH = 10h
                DL = Drive number (Bit 7 must be set)

        Return  AH = Status of operation (See Service 01h)
                CF   Set if error, else cleared

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    If the fixed disk drive is ready, then AH is 0 and the Carry Flag
    is clear.

    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.