The following information is for reference only:
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Directory Entries
File Attribute Byte
FAT16 Structure (FAT16 Structure)
Disk boot recording structure (boot record layout)
Directory Entries
offset length description format comments 00H 8 bytes filename ASCII chars, or special code if first char: 00H = name never used 05H = first character or name is realy E5H E5H = file was used, but has been erased 2EH = entry is a directory must be padded with spaces to fill field 08H 3 bytes file type (extension) ASCII chars must be padded with spaces to fill field 0BH byte file attribute bit codes: bit0 = read-only bit1 = hidden bit2 = system bit3 = volumn label bit4 = directory bit5 = archive bit6 = unused bit7 = unused 0CH 10 bytes reserved 16H word time file last updated coded word: (unsigned 16 bit-bit integer) time = Hr * 2048 Min * 32 Sec 2 *: least significant byte first 18H word date file last updated coded word: (unsigned 16 bit-bit integer) time = (Yr-1980) * 512 Mon * 32 Day *: least significant byte first 1AH word starting cluster number word binary integer * 1CH dbl word file Size Double Word Binary Integer *
Directory Entries
File Attribute Byte
FAT16 Structure (FAT16 Structure)
Disk boot recording structure (boot record layout)
File Attribute Byte
76543210meaning if set to 1meaning if set to 0 vread-only fileread / write file v hidden filevisible file v system fileregular file v volumn nameregular file v directory nameregular file v file changed since last backupfile unchanged since last backupvv reservedreserved
Directory Entries
File Attribute Byte
FAT16 Structure (FAT16 Structure)
Disk boot recording structure (FAT16 Structure):
Entry Example Value Use 0 FFF8 Disk ID byte 1 FFFF Filler 2 0003 Cluster value: 0000 = unused cluster 0002-ffff = next cluster number fff0-fff6 = reserved cluster fff7 = cluster marked bad fff8-ffff = last cluster in file 3 0004 4 0005 5 FFFF 6 0000
Directory Entries
File Attribute Byte
FAT16 Structure (FAT16 Structure)
Disk boot recording structure (boot record layout)
Disk boot recording structure (boot record layout)
DOS3.3 and DOS4.0 Boot Record Layout
offsetlengthdescriptionDOS version003 bytesJMP to boot code 038 bytesOEM name and version 0Bwordbytes per sector 0Dbytesectors per cluster (must be a power of 2) 0Ewordreserved sectors (for Dir, FAT, etc.) 10byteNumber of copies of FAT 11wordMaximum number directory of root entries 13wordTotal number of sectors in logical image 15byteMedia descriptor byte 16wordnumber of sectors in FAT 18wordnumber of sectors per track 1Awordnumber of heads 1Cwordnumber of hidden sectors 1EwordHO number of hidden sectors 20dbl wordnumber of logical sectors
DOS5.0 Boot Sector Structru
offset length description DOS version 1E dbl word number of hidden sectors DOS 5.0 boot sector structure 22 dbl word number of sectors if the size of the drive is larger than 32MB 23 byte drive number used Internally by DOS 24 byte reserved 25 byte boot signature. always 29H. 29 DBL Word Volumn ID Number 34 11 bytes Volumn Label 3C 8 BYTES FILE-SYSTEM TYPE
Directory Entries
File Attribute Byte
FAT16 Structure (FAT16 Structure)
Disk boot recording structure (boot record layout)
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