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                           Media Descriptor Byte

      Media Descriptor Byte Layout:

        |7|6|5|4|3|2|1|0| IBM Media Descriptor Byte
         | | | | | | | +--- 1 = 2 sided, 0 = not 2 sided
         | | | | | | +---- 1 = 8 sector, 0 = not 8 sector
         | | | | | +----- 1 = removable, 0 = not removable
         +-------------- must be set to 1

        F8      Hard disk
                Double sided  18 sector diskette  PS/2 1.44 Mb. DSQD

        F9      5.  Double sided, High Density diskette (15 sector)
                3.  Double Sided, Double High Density diskette (9 sector)

        FA      Ram disk (not all Ramdisks use this)

        FC      5. Single Sided, Double Density diskette (9 sector)
                8  inch Double Sided, Single Density diskette

        FD      5. Double Sided, Double Density (9 sector)
                8  inch Double Sided Single Density (26 sector) (IBM 3740
                   format) 128 bytes per sector, soft sector, 4 sectors
                   cluster, 4 reserved sectors, 2 FATs, 68 directory entries,
                   77*26*2 sectors.

        FE      5. Single Sided, Double Density diskette (8 sector)
                8  inch Single Sided, Single Density diskette (26 sector)
                   (IBM 3740 format) 128 bytes per sector, soft sector,
                   4 sectors per cluster, 1 reserved sector, 2 FATs. 68
                   directory entries, 77*26 sectors.
                8  inch Double Sided, Double Density (8 sector), 1024 bytes
                   per sector, soft sector, 1 sector per cluster, 1 reserved
                   sector, 2 FATs, 192 directory entries, 77*8*2 sectors. To
                   distinguish from 8 inch SS/SD attempt read of side 2.

        FF      5. Double Sided, Double Density diskette (8 sector)

        - see also   INT 21,1B  INT 21,1C  FAT