UMBC CMSC 211

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Disk Parameter Block (DPB)

Disk Parameter Block Definition
OffsetSizeDescription
00h1Drive number (0=A:,1=B:,etc)
01h1unit number within device driver
02h2bytes per sector
04h1highest sector number within cluster
05h1shift count to convert clusters into sectors
06h2number of reserved sectors at beginning of drive
08h1number of FATs
09h2number of root directory entries
0Bh2number of first sector containing user data
0Dh2highest cluster number (number of clusters + 1)
0Fh2number of sectors per FAT
11h2sector number of first directory sector
13h2address of device driver header
17h1media ID byte
18h100h if disk is accessed, FF if not
19h4pointer to next DPB
1Dh2cluster at which to start search for free space when writing
1Fh2number of free clusters on drive, FFFFh = not known


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