{"id":627,"date":"2015-10-18T14:39:00","date_gmt":"2015-10-18T06:39:00","guid":{"rendered":"http:\/\/note.systw.net\/note\/?p=627"},"modified":"2023-11-04T14:48:36","modified_gmt":"2023-11-04T06:48:36","slug":"filesystem-fat","status":"publish","type":"post","link":"https:\/\/systw.net\/note\/archives\/627","title":{"rendered":"FileSystem FAT"},"content":{"rendered":"\n


FAT<\/strong>
FAT12: Developed 1977 (MS Disk BASIC)
FAT16: Developed 1987 (MS-DOS 3.31)
FAT32: Developed 1996 (Win95 OSR2)
exFAT<\/p>\n\n\n\n

refer
http:\/\/www.c-jump.com\/CIS24\/Slides\/FAT\/lecture.html  <\/p>\n\n\n\n

ps:
FAT12 is most suitable for very small volumes, and is used on floppy disks and hard disk partitions smaller than about 16 MB\u3000
refer
http:\/\/www.pcguide.com\/ref\/hdd\/file\/partSizes-c.html<\/p>\n\n\n\n

…………………………………………………………………………………………….<\/p>\n\n\n\n

FAT32<\/strong><\/p>\n\n\n\n

limit of FAT32<\/strong>
limit of volume size is 2TB
limit of a file size is 4GB<\/p>\n\n\n\n

cluster<\/strong>
windows \u7684\u78c1\u789f\u55ae\u4f4d
FAT32\u9810\u8a2d\u662f1\u500bcluster\u4f54\u75284\u500bsector(2KB)
ex:
\u82e5\u6a94\u6848\u70ba125KB,\u90a3\u6703\u9700\u898162.5\u500bcluster.\u56e0\u6b64\u8981\u4f54\u752863\u500bcluster
\u800c63\u500bcluster\u4f54\u7528\u5c31=256\u500bsector\u88ab\u4f54\u7528
ps:
\u82e5\u6a94\u6848\u5c0f\u65bc1\u500bcluster,\u5176\u9918\u7684\u7a7a\u9593\u4e5f\u7121\u6cd5\u4f7f\u7528,\u9019\u4e9b\u7a7a\u9593\u7a31\u70baslack space<\/p>\n\n\n\n

…<\/p>\n\n\n\n


FAT Partition boot sector<\/strong>
first sector in the partition
structure as below
\u30003byte, jump instruction
\u30008byte, OEM name in text
\u300025byte, BIOS parameter block
\u300026byte, Extended BIOS parameter block
\u3000448byte, Bootstrap Code
\u30002 byte, end of sector marker<\/p>\n\n\n\n

…<\/p>\n\n\n\n

FAT layout<\/strong>
Root directory(directory entries)
File allocation table(FAT1)
File allocation table for backup(FAT2)<\/p>\n\n\n\n

FAT ID of FAT1<\/strong>
0x0000:unused\/unallocated cluster
0xFFF7: bad cluster
0x:FFFB-0xFFFF: Last cluster in a file
ps:
ID is 1word(2byte)
ps:
\u8a08\u7b97\u6709\u591a\u5c11last cluster\u53ef\u77e5\u9053\u6709\u5e7e\u500b\u6a94\u6848<\/p>\n\n\n\n

structure of root directory\u3000<\/strong>
[0] 1byte, status(0xe5=delete,0x00=unallocated)
[0-10] file name in ASCII
[11] file attribute
[12] reserved
[13] create time(tenths of second)
[14-15] create time(hours,minutes,seconds)
[16-17] created day
[18-19] accessed day
[20-21] high 2 bytes of first cluster address 
[22-23] written time(hours,minutes,seconds)
[24-25] written day
[26-27] low 2 bytes of first cluster address , \u8a18\u9304\u8cc7\u6599\u90a3\u5f9e\u88e1\u958b\u59cb\u8a18\u9304
[28-31] 4byte, size of file, 0=directory
ps:
FAT\u6c92\u6709accessed time
filename\u683c\u5f0f\u70ba”6char”+”~1.\u526f\u6a94\u540d”, \u82e5\u6709\u91cd\u8986\u5247\u589e\u52a0\u5e8f\u865f\u70ba”6char”+”~2.\u526f\u6a94\u540d”
ps:
make file disappear, set first character to 0xE5 or 0x00<\/p>\n\n\n\n


file attribute<\/strong>
Flag = Value, Description, Essential
0000 0001 = 0x01, Read only, No
0000 0010 = 0x02, Hidden file, No
0000 0100 = 0x04, System file, No
0000 1000 = 0x08, Volume label, Yes
0000 1111 = 0x0f, Long file name, Yes
0001 0000 = 0x10, Directory, Yes
0010 0000 = 0x20, Archive, No<\/p>\n\n\n\n

…<\/p>\n\n\n\n

Lost clusters<\/strong>
\u4ee5\u4e0b\u5169\u60c5\u6cc1\u540c\u6642\u767c\u751f\u6642\u8868\u793acluster\u907a\u5931
OS does not allocate cluster to any file, ex:a file is deleted from the directory listing
OS marks cluster as used, ex:FAT still shows the clusters allocated to the file<\/p>\n\n\n\n

… <\/p>\n\n\n\n

chkdisk<\/strong>
\u6aa2\u67e5\u76ee\u9304\u7d50\u69cb\u548c FAT \u4e0d\u4e00\u81f4\u6027\u7684\u5de5\u5177
\u53ef\u6aa2\u67e5\u4ee5\u4e0b:
\u3000\u7121\u6548\u7684\u6307\u6a19\u5230\u8cc7\u6599\u5340\u57df
\u3000\u76ee\u9304\u9805\u76ee\u4e2d\u7684\u4e0d\u6b63\u78ba\u7684\u6a94\u6848\u5c6c\u6027
\u3000\u640d\u58de\uff0c\u56e0\u6b64\u7121\u6cd5\u6aa2\u67e5\u4e00\u6216\u591a\u500b\u8def\u5f91\u7684\u76ee\u9304\u7684\u4e00\u90e8\u4efd
\u3000\u6574\u500b\u76ee\u9304\uff0c\u8b93\u8a72\u76ee\u9304\u4e2d\u6240\u5305\u542b\u7684\u6a94\u6848\u7121\u6cd5\u5b58\u53d6\u7684\u640d\u58de
\u3000\u5728 FAT \u640d\u58de\u7684\u78c1\u789f\u78c1\u6247\u5340
\u3000Invalid cluster numbers in the FAT(\u7121\u6548\u7684\u53e2\u96c6\u5728FAT)
\u3000Lost Cluster(\u907a\u5931\u53e2\u96c6):\u53e2\u96c6\u8b58\u5225\u672a\u88ab\u6307\u6d3e\u81f3\u6a94\u6848
\u3000\u4ea4\u4e92\u9023\u7d50\u7684\u6a94\u6848\u76f8\u540c\u7684\u53e2\u96c6 (\u8d85\u904e\u4e00\u500b\u6a94\u6848\u5df2\u88ab\u6307\u6d3e\u76f8\u540c\u7684\u53e2\u96c6)
refer
(https:\/\/support.microsoft.com\/zh-tw\/kb\/71609)<\/p>\n","protected":false},"excerpt":{"rendered":"

FATFAT12: Developed 1977 (MS D …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"fifu_image_url":"","fifu_image_alt":"","_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[18],"tags":[],"class_list":["post-627","post","type-post","status-publish","format-standard","hentry","category-windows"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts\/627","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/comments?post=627"}],"version-history":[{"count":0,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts\/627\/revisions"}],"wp:attachment":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/media?parent=627"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/categories?post=627"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/tags?post=627"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}