Leaked source code of windows server 2003
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BREAK <DPB structure>
;; Microsoft Confidential; Copyright (C) Microsoft Corporation 1991; All Rights Reserved.;
;** DPB - Drive Parameter Block;; BUGBUG - this isn't authorative - it's my probably incomplete and; possibly inaccurate deductions from code study... - jgl;; The DPB is DOS's main structure for describing block devices.; It contains info about the "Drive" intermingled with info about; the FAT file system which is presumably on the drive. I don't know; how those fields are used if it's not the FAT file system - BUGBUG;; The DPBs are statically allocated and chained off of DPBHead.; Users scan this chain looking for a match on DPB_DRIVE.; The DPBs are built at init time from info in the SYSDEV structure.
DPB STRUC
DPB_DRIVE DB ? ; Logical drive # assoc with DPB (A=0,B=1,...)DPB_UNIT DB ? ; Driver unit number of DPBDPB_SECTOR_SIZE DW ? ; Size of physical sector in bytesDPB_CLUSTER_MASK DB ? ; Sectors/cluster - 1DPB_CLUSTER_SHIFT DB ? ; Log2 of sectors/clusterDPB_FIRST_FAT DW ? ; Starting record of FATsDPB_FAT_COUNT DB ? ; Number of FATs for this driveDPB_ROOT_ENTRIES DW ? ; Number of directory entriesDPB_FIRST_SECTOR DW ? ; First sector of first clusterDPB_MAX_CLUSTER DW ? ; Number of clusters on drive + 1DPB_FAT_SIZE DW ? ; Number of records occupied by FATDPB_DIR_SECTOR DW ? ; Starting record of directoryDPB_DRIVER_ADDR DD ? ; Pointer to driverDPB_MEDIA DB ? ; Media byteDPB_FIRST_ACCESS DB ? ; This is initialized to -1 to force a media ; check the first time this DPB is usedDPB_NEXT_DPB DD ? ; Pointer to next Drive parameter blockDPB_NEXT_FREE DW ? ; Cluster # of last allocated clusterDPB_FREE_CNT DW ? ; Count of free clusters, -1 if unknown
DPB ENDS
DPBSIZ EQU SIZE DPB ; Size of the structure in bytes
DSKSIZ = DPB_max_CLUSTER ; Size of disk (temp used during init only)
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