DOS defines a 1-byte code that (sometimes) can be used to identify the type of media that is being used by a disk device. The Media Descriptor (also called the FAT ID byte) will be seen: ■ as a value obtained from DOS Fns 1bH, 1cH, and 32H ■ as the first byte of the FAT (DOS logical sector 1) ■ at offset 0aH of a BPBRec ■ at offset 15H of a BootSectorRec (in DOS logical sector 0) ■ in the data block used by DOS Fn 440dH (Generic IOCTL) Value Media Types Defined as of DOS 5.0 ▀▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ f0H 3½" (1.44 MB) 2 sides, 18 sectors 3½" (2.88 MB 2 sides, 36 sectors 5¼" (1.2 MB) 2 sides, 15 sectors (also used for other media types) f8H fixed disk, any capacity f9H 3½" (720K) 2 sides, 9 sectors, 80 tracks 5¼" (1.2 MB) 2 sides, 15 sectors, 80 tracks faH 5¼" (320K) 1 side, 8 sectors, 80 tracks fbH 3½" (640K) 2 sides, 8 sectors, 80 tracks fcH 5¼" (180K) 1 side, 9 sectors, 40 tracks fdH 5¼" (360K) 2 sides, 9 sectors, 40 tracks; also used on 8" disks feH 5¼" (160K) 1 side, 8 sectors, 40 tracks; also used on 8" disks ffH 5¼" (320K) 2 sides, 8 sectors, 40 tracks The media descriptor byte is not a particularly reliable way to ascertain media type. Refer to other fields of the BPBRec or BootSectorRec to obtain track, sector, and head information. For instance, the boot sector of a RAM disk may show it to be a hard disk (f8H) or even some other value. See Also: fn 1bH and fn 1cH (get FAT info) fn 32H (get drive parameter block) BPBRec Device Drivers (see DvRq 01H and DvRq 02H) -♦-