BOOT,FAT16结构

最新推荐文章于 2025-07-02 20:00:01 发布

原创最新推荐文章于 2025-07-02 20:00:01 发布 · 334 阅读

CC 4.0 BY-SA版权

文章标签：

本文详细介绍了FAT16文件系统的内部结构，包括目录项的布局、文件属性字节的意义、FAT16的具体结构及磁盘引导记录的布局等内容。通过对这些关键组成部分的分析，帮助读者理解FAT16文件系统的运作原理。

以下资料仅供参考:

----------------------------------------------------------------------------------------

目录项(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=Hr2048+Min32+Sec+2	*:least significant byte first
18H	word	date file last updated	coded word:(unsigned 16 bit-bit integer) time=(Yr-1980)512+Mon32+Day	*:least significant byte first
1AH	word	starting cluster number	word binary integer*
1CH	dbl word	file size	double word binary integer*

文件属性字节(File attribute byte)

7	6	5	4	3	2	1	0	meaning if set to 1	meaning if set to 0
							v	read-only file	read/write file
						v		hidden file	visible file
					v			system file	regular file
				v				volumn name	regular file
			v					directory name	regular file
		v						file changed since last backup	file unchanged since last backup
v	v							reserved	reserved

FAT16结构(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

dos3.3 and dos4.0 BOOT record layout

offset	length	description	DOS version
00	3 bytes	JMP to boot code
03	8 bytes	OEM name and version
0B	word	bytes per sector
0D	byte	sectors per cluster(must be a power of 2)
0E	word	reserved sectors(for Dir,FAT,etc.)
10	byte	Number of copies of FAT
11	word	Maximum number of root directory entries
13	word	Total number of sectors in logical image
15	byte	Media descriptor byte
16	word	number of sectors in FAT
18	word	number of sectors per track
1A	word	number of heads
1C	word	number of hidden sectors
1E	word	HO number of hidden sectors
20	dbl word	number of logical sectors

DOS5.0 BOOT sector structrure

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

----------------------------------------------------------------------------------------