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Operating_systems-page57 - 32 Floppy disk Fig 6 Floppy disk...

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Jelena Mamčenko Operating Systems Lecture Notes on Operating Systems 57 0x?FFFFFF6 0xFF7 0xFFF7 0x?FFFFFF7 Bad cluster 0xFF8 - 0xFFF 0xFFF8 - 0xFFFF 0x?FFFFFF8 - 0x?FFFFFFF Last cluster in file Note that FAT32 uses only 28 bits of the 32 possible bits. The upper 4 bits are usually zero but are reserved and should be left untouched. In the table above these are denoted by a question mark. The first cluster of the data area is cluster #2. That leaves the first two entries of the FAT unused. In the first byte of the first entry a copy of the media descriptor is stored. The remaining bits of this entry are 1. In the second entry the end-of-file marker is stored. The high order two bits of the second entry are sometimes, in the case of FAT16 and FAT32, used for dirty volume management: high order bit 1: last shutdown was clean; next highest bit 1: during the previous mount no disk I/O errors were detected. [6]
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Unformatted text preview: 32 Floppy disk Fig. 6. Floppy disk A floppy disk is a data storage device that is composed of a ring of thin, flexible (i.e. "floppy") magnetic storage medium encased in a square or rectangular plastic wallet. Floppy disks are read and written by a floppy disk drive or FDD , the latter initialism not to be confused with "fixed disk drive", which is an old IBM term for a hard disk drive. Floppy disk format Year introduced Storage capacity (binary kilobytes if not stated) Marketed capacity¹ 8-inch (read-only) 1969 80 ← 8-inch 1972 183.1 1.5 Megabit 8-inch 1973 256 256 KB 8-inch DD 1976 500 0.5 MB 5¼-inch (35 track) 1976 89.6 110 KB 8-inch double sided 1977 1200 1.2 MB 5¼-inch DD 1978 360 360 KB 3½-inch HP single sided 1982 280 264 KB 3-inch 1982 ] 360 ← 3½-inch (DD at release) 1984 720 720 KB 5¼-inch QD 1984 1200 1.2 MB 3-inch DD 1984 720 ← 3-inch Mitsumi Quick Disk 1985 128 to 256 ←...
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