File Allocation Table (FAT) is a partially patented file system developed by Microsoft for MS-DOS and was the primary file system for consumer versions of Microsoft Windows up to and including Windows Me. FAT as it applies to flexible/floppy and optical disk cartridges (FAT12 and FAT16 without long file name support) has been standardized as ECMA-107 and ISO/IEC 9293. For other uses, see Patent (disambiguation). ... It has been suggested that Crash counting be merged into this article or section. ... Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... Windows redirects here. ... Windows Millennium Edition, or Windows Me (IPA pronunciation: [miː], [ɛm iː]), is a hybrid 16-bit/32-bit graphical operating system released on September 14, 2000 by Microsoft. ...

The FAT file system is relatively uncomplicated, and is supported by virtually all existing operating systems for personal computers. This ubiquity makes it an ideal format for floppy disks and solid-state memory cards, and a convenient way of sharing data between disparate operating systems installed on the same computer (a dual boot environment). // An operating system (OS) is the software that manages the sharing of the resources of a computer. ... A floppy disk is a data storage device that is composed of a disk of thin, flexible (floppy) magnetic storage medium encased in a square or rectangular plastic shell. ... Solid state may refer to: In computing: Solid state devices are data storage device components that uses memory chips, such as SDRAMs, to store data. ... This article does not cite any references or sources. ... Dual booting or dual-booting is the act of installing multiple operating systems on a computer, and choosing which one when it boots. ...

The most common implementations have a serious drawback in that when files are deleted and new files written to the media, directory fragments tend to become scattered over the entire media, making reading and writing a slow process. Defragmentation is one solution to this, but is often a lengthy process in itself and has to be performed regularly to keep the FAT file system clean. In the context of administering computer systems, defragmentation is a process that reduces the amount of fragmentation in file systems. ...

For other uses, see Software developer (disambiguation). ... Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... Microsoft BASIC is the foundation product of the Microsoft company. ... Compaq Computer Corporation is an American personal computer company founded in 1982, and now a brand name of Hewlett-Packard. ... Windows 95 is a consumer-oriented graphical user interface-based operating system. ... In computer engineering, hard disk drive partitioning is the creation of logical divisions upon a hard disk that allows one to apply operating system-specific logical formatting. ... A Master Boot Record (MBR), or partition sector, is the 512-byte boot sector that is the first sector (Sector 0) of a partitioned data storage device such as a hard disk. ... A Master Boot Record (MBR), or partition sector, is the 512-byte boot sector that is the first sector (Sector 0) of a partitioned data storage device such as a hard disk. ... A Master Boot Record (MBR), or partition sector, is the 512-byte boot sector that is the first sector (Sector 0) of a partitioned data storage device such as a hard disk. ... GUID Partition Table (GPT) is a standard for the layout of the partition table on a physical hard disk. ... A mebibyte (a contraction of mega binary byte) is a unit of information or computer storage, abbreviated MiB. 1 MiB = 220 bytes = 1,048,576 bytes = 1,024 kibibytes 1 MiB = 1024 (= 210) kibibytes (KiB), and 1024 MiB equal one gibibyte (GiB). ... A gibibyte is a unit of information or computer storage. ... A gibibyte is a unit of information or computer storage. ... A 8. ... Long filename is the name given to the longer and therefore more descriptive titles on the FAT filesystem, which was previously restricted to eight characters and a three-character extension (referred to as 8. ... A mebibyte (a contraction of mega binary byte) is a unit of information or computer storage, abbreviated MiB. 1 MiB = 220 bytes = 1,048,576 bytes = 1,024 kibibytes 1 MiB = 1024 (= 210) kibibytes (KiB), and 1024 MiB equal one gibibyte (GiB). ... A gibibyte is a unit of information or computer storage. ... A gibibyte is a unit of information or computer storage. ... A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes... A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes... is the 1st day of the year in the Gregorian calendar. ... Year 1980 (MCMLXXX) was a leap year starting on Tuesday (link displays the 1980 Gregorian calendar). ... is the 365th day of the year (366th in leap years) in the Gregorian calendar. ... (Redirected from 2107) (21st century - 22nd century - 23rd century - other centuries) The twenty-second century comprises the years 2101 to 2200. ... In computer file systems, a fork is additional data associated with a file system object. ... An archive bit is a file attribute present in many computer file systems, notably FAT, FAT32, and NTFS. The purpose of an archive bit is to track incremental changes to files for the purpose of backup (also called archiving). ... Most modern file systems have methods of administering permissions or access rights to specific users and groups of users. ... Stac Electronics was an engineering company founded in 1984 by four friends at Caltech. ... DoubleSpace was the original name of the disk compression software that was supplied with MS-DOS starting from version 6. ... This article contains information that has not been verified and thus might not be reliable. ... This article does not cite any references or sources. ...

History

The FAT filesystem was created by Bill Gates and Marc McDonald in 1977 for managing disks in Microsoft Disk BASIC. In August 1980 Tim Paterson incorporated FAT into his 86-DOS operating system for the S-100 8086 CPU boards;^[1] the filesystem was the main difference between 86-DOS and its predecessor, CP/M. For other persons named Bill Gates, see Bill Gates (disambiguation). ... Was Microsofts first employee. ... Microsoft BASIC is the foundation product of the Microsoft company. ... Tim Paterson (born 1956) is an American computer programmer, best known as the original author of the popular MS-DOS operating system. ... 86-DOS was an operating system developed and marketed by Seattle Computer Products for its Intel 8086-based computer kit. ... The S-100 bus, IEEE696-1983 (withdrawn), was an early computer bus designed in 1974 as a part of the Altair 8800, generally considered today to be the first personal computer. The S-100 bus was the first industry standard bus for the microcomputer industry, and S-100 computers, processor... The 8086 is a 16-bit microprocessor chip designed by Intel in 1978, which gave rise to the x86 architecture. ... CP/M was an operating system originally created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc. ...

The name originates from the usage of a table which centralizes the information about which areas belong to files, are free or possibly unusable, and where each file is stored on the disk. To reduce the management complexity, disk space is allocated to files in contiguous groups of hardware sectors called clusters. The maximum possible number of clusters has dramatically increased over time, and the number of bits required to identify a cluster is used to name the successive major versions of the format. The FAT standard has also evolved in several ways where backward compatibility with existing software has been preserved. In certain filesystem types like the File Allocation Table (FAT) filesystem of MS-DOS or the NTFS filesystem of Windows NT, a cluster is the unit of disk space allocation for files and directories. ...

FAT12

This initial version of FAT is now referred to as FAT12. As a filesystem for floppy disks, it had a number of limitations: cluster addresses were "only" 12 bits long (which limited cluster count to 4096 and made FAT manipulation a bit tricky) and the disk size was stored as a 16-bit count of sectors, which limited the size to 32 MB. FAT12 was used by several manufacturers with different physical formats but a typical floppy diskette at the time was 5.25", single-sided, 40 tracks, with 8 sectors per track, resulting in a capacity of slightly less than 160 KB. The FAT12 limitations exceeded this capacity by one or more orders of magnitude, the limits were successively lifted in the following years which increased storage capacity dramatically but eventually rendered FAT12 obsolete. It has been suggested that Disk sector be merged into this article or section. ... It has been suggested that Disk sector be merged into this article or section. ...

By convention all the control structures were organised to fit inside the first track, thus avoiding head movement during read and write operations, although this varied depending on the manufacturer and physical format of the disk. Since when FAT12 was introduced DOS had no support for hierarchical directories the maximum number of files was typically limited to a few dozen.

A limitation which was not addressed until much later was that any bad sector in the control structures area, track 0, could prevent the diskette from being usable. The DOS formatting tool rejected such diskettes completely. Bad sectors were only allowed in the file area, where they made the entire holding cluster unusable as well.

Directories

In March 1983, IBM launched the PC XT computer, which featured a 10 MB hard disk. MS-DOS/PC-DOS 2.0 was released simultaneously, and introduced hierarchical directories to properly support the "massive" capacity the new medium provided. Apart from allowing for better organization of files, directories allowed it to store many more files on the hard disk, as the maximum number of files was no longer constrained by the (still fixed) root directory size. This number could now be equal to the number of clusters (or even greater, given that zero-sized files do not use any clusters on FAT). The IBM Personal Computer XT, often shortened to the PC XT or simply XT, was IBMs successor to the original IBM PC. It was released as IBM product number 5160 on March 8, 1983, and was one of the first computers to come standard with a hard drive. ...

The format of the FAT itself did not change. The 10 MB hard disk on the PC XT had 4 KB clusters. If a 20 MB hard disk was later installed, and formatted with MS-DOS 2.0, the resultant cluster size would be 8 KB, the boundary at 15.9 MiB.

Initial FAT16

In 1984 IBM released the PC AT, which featured a 20 MB hard disk. Microsoft introduced MS-DOS 3.0 in parallel. Cluster addresses were increased to 16-bit, allowing for a greater number of clusters (up to 65,517) and consequently much greater file-system sizes. However, the maximum possible number of sectors and the maximum (partition, rather than disk) size of 32 MB did not change. Therefore, although technically already "FAT16", this format was not yet what today is commonly understood under this name. A 20 MB hard disk formatted under MS-DOS 3.0 was not accessible by the older MS-DOS 2.0. Of course, MS-DOS 3.0 could still access MS-DOS 2.0 style 8 KB cluster partitions. The IBM Personal Computer/AT (IBM 5170), more commonly known as the IBM AT and also sometimes called the PC AT or PC/AT, was IBMs second-generation PC, designed around the Intel 80286 microprocessor running at 6 MHz and released in 1984. ...

MS-DOS 3.0 also introduced support for high-density 1.2 MB 5.25" diskettes, which notably had 15 sectors per track, hence more space for FAT. This probably prompted a dubious optimization of the cluster size, which went down from 2 sectors to just 1. The net effect was that high density diskettes were significantly slower than older double density ones.

Extended partition and logical drives

Apart from improving the structure of the FAT filesystem itself, a parallel development allowing an increase in the maximum possible FAT storage space was the introduction of multiple FAT partitions. Originally partitions were supposed to be used only for sharing the disk between operating systems, typically DOS and Xenix at the time, so DOS was only prepared to handle one FAT partition. It was not possible to create multiple DOS partitions using DOS tools, and third party tools would warn that such a scheme would not be compatible with DOS. Simply allowing several identical-looking DOS partitions could lead to naming problems: should C: be the first FAT partition on disk, for simplicity, or rather the partition marked as active in the partition table, so that several DOS versions can co-exist? And which partition should be C: if the system was booted from a diskette? Xenix was a version of the Unix operating system, licensed by Microsoft from AT&T in the late 1970s. ...

To allow the use of more FAT partitions in a compatible way, a new partition type was introduced (in MS-DOS 3.2, January 1986), the extended partition; which was actually just a container for additional partitions called logical drives. Originally only 1 logical drive was possible, allowing the use of hard disks up to 64 MB. In MS-DOS 3.3 (August 1987) this limit was increased to 24 drives; it probably came from the compulsory letter-based disk naming (A and B being reserved for the two floppy drives). The logical drives were described by on-disk structures which closely resemble the Master Boot Record (MBR) of the disk (which describes the primary partitions), probably to simplify coding. Though some believe these partitions were nested in a way analogous to Russian matryoshka dolls, that wasn't the case. They were always stored on disk like a row of separate blocks within a single box; these blocks are often referred to as being chained together, by the links in their EBR sectors. Only one extended partition was allowed. Logical drives were not bootable, and the extended partition could only be created after the primary FAT partition (except with third party formatting tools), which removed all ambiguity, but also the possibility of booting several DOS versions from the same hard disk. An Extended Boot Record (EBR) is a descriptor for a logical partition in the common DOS disk drive partitioning system. ... A Master Boot Record (MBR), or partition sector, is the 512-byte boot sector that is the first sector (Sector 0) of a partitioned data storage device such as a hard disk. ... This article is about the Russian doll. ...

A useful side-effect of the extended partition scheme was to significantly increase the maximum number of partitions possible on a PC hard disk, beyond the 4 which could be described by the MBR alone.

Prior to the introduction of extended partitions, some hard disk controllers (which at that time were separate option boards, since the IDE standard did not yet exist) could make large hard disks appear as two separate disks. ATA cables: 40 wire ribbon cable top, 80 wire ribbon cable bottom Advanced Technology Attachment (ATA) is a standard interface for connecting storage devices such as hard disks and CD-ROM drives inside personal computers. ...

Final FAT16

Finally in November 1987, Compaq DOS 3.31 introduced what is today called the FAT16 format, with the expansion of the 16-bit disk sector index to 32 bits. The result was initially called the DOS 3.31 Large File System. Although the on-disk changes were apparently minor, the entire DOS disk code had to be converted to use 32-bit sector numbers, a task complicated by the fact that it was written in 16-bit assembly language. Compaq Computer Corporation is an American personal computer company founded in 1982, and now a brand name of Hewlett-Packard. ... See the terminology section, below, regarding inconsistent use of the terms assembly and assembler. ...

In 1988 the improvement became more generally available through MS-DOS 4.0 and OS/2 1.1. The limit on partition size was now dictated by the 8-bit signed count of sectors-per-cluster, which had a maximum power-of-two value of 64. With the usual hard disk sector size of 512 bytes, this gives 32 KB clusters, thereby fixing the "definitive" limit for the FAT16 partition size at 2 gibibytes. On magneto-optical media, which can have 1 or 2 KiB sectors, the limit is proportionally greater. To meet Wikipedias quality standards, this article or section may require cleanup. ... A gibibyte is a unit of information or computer storage. ... Magneto-optical disc A Magneto-optical disc and the numerous rectangles on its surface A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon magneto-optical discs. ...

Much later, Windows NT increased the maximum cluster size to 64 KB by considering the sectors-per-cluster count as unsigned. However, the resulting format was not compatible with any other FAT implementation of the time, and it generated massive internal fragmentation. Windows 98 also supported reading and writing this variant, but its disk utilities didn't work with it. Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... In computer storage, there are three related uses of the term fragmentation: external fragmentation, internal fragmentation, and data fragmentation, all related to storage. ... Windows 98 (codenamed Memphis and formerly known as Windows 97[2]) is a graphical operating system released on June 25, 1998 by Microsoft and the successor to Windows 95. ...

The number of root directory entries available is set at formatting time, and is stored in a 16 bit signed field setting an absolute limit of 32767 entries (32736, a multiple of 32, in practice). For historical reasons, FAT12 and FAT16 media generally use 512 root directory entries on non-floppy media, and other sizes may be incompatible with some software or devices (entries being file and/or folder names in the old 8.3 format).^[2] Some third party tools like mkdosfs allow the user to set this parameter.^[3]

Long File Names (VFAT, LFNs)

One of the "user experience" goals for the designers of Windows 95 was the ability to use long filenames (LFNs - up to 255 UTF-16 characters long), in addition to classic 8.3 filenames. LFNs were implemented using a work-around in the way directory entries are laid out (see below). The version of the file system with this extension is usually known as VFAT after the Windows 95 VxD device driver, also known as "Virtual FAT" in Microsoft's old document. User experience is a term used to describe the overall experience and satisfaction a user has when using a product or system. ... Windows 95 is a consumer-oriented graphical user interface-based operating system. ... Long filename is the name given to the longer and therefore more descriptive titles on the FAT filesystem, which was previously restricted to eight characters and a three-character extension (referred to as 8. ... A 8. ... A workaround is a bypass of a recognized problem in a system. ... In Microsoft computing, a VxD is a virtual device driver. ...

Interestingly, the VFAT driver actually appeared before Windows 95, in Windows for Workgroups 3.11, but was only used for implementing 32-bit File Access, a higher performance protected mode file access method, bypassing DOS and directly using either the BIOS, or, better, the Windows-native protected mode disk drivers. A typical Windows 3. ... 32-bit file access refers to the higher performance, protected mode disk caching method introduced in Windows for Workgroups 3. ... Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later. ... This article does not cite any references or sources. ...

In Windows NT, support for long filenames on FAT started from version 3.5. OS/2 added long filename support to FAT using extended attributes (EA) before the introduction of VFAT; thus, VFAT long filenames are invisible to OS/2, and EA long filenames are invisible to Windows. Windows NT 3. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Extended file attributes is a file system feature that enables users to associate with computer files metadata not interpreted by the filesystem, whereas regular attributes have a purpose strictly defined by the filesystem (such as permissions or records of creation and modification times). ...

FAT32

In order to overcome the volume size limit of FAT16, while still allowing DOS real-mode code to handle the format without unnecessarily reducing the available conventional memory, Microsoft decided to implement a newer generation of FAT, known as FAT32, with cluster counts held in a 32-bit field, of which 28 bits are currently used. Conventional memory is the first 640 kibibytes of an IBM PCs memory. ...

In theory, this should support a total of approximately 268,435,456 (2²⁸) clusters, allowing for drive sizes in the range of 8 terabytes with 32K clusters, but the boot sector uses a 32 bit field to limit volume size to 2³² sectors (2TB on a hard disk with 512 byte sectors). See this article by Raymond Chen. This article is about a measurement term for data storage capacity. ...

On Windows 95/98, due to the version of Microsoft's ScanDisk utility included with these operating systems being a 16-bit application, the FAT structure is not allowed to grow beyond 4,177,920 (< 2²²) clusters, placing the volume limit at 127.53 gigabytes.^[4]. A limitation in original versions of Windows 98/98SE's Fdisk causes it to incorrectly report disk sizes over 64GB.^[5] A corrected version is available from Microsoft. These limitations do not apply to Windows 2000/XP except during Setup, in which there is a 32GB limit.^[6] Windows ME supports the FAT32 file system without any limits.^[7] This article does not cite any references or sources. ... This article is about the unit of measurement. ...

FAT32 was introduced with Windows 95 OSR2, although reformatting was needed to use it, and DriveSpace 3 (the version that came with Windows 95 OSR2 and Windows 98) never supported it. Windows 98 introduced a utility to convert existing hard disks from FAT16 to FAT32 without loss of data. In the NT line, native support for FAT32 arrived in Windows 2000. A free FAT32 driver for Windows NT 4.0 was available from Winternals, a company later acquired by Microsoft. Since the acquisition the driver is no longer officially available. This article contains information that has not been verified and thus might not be reliable. ... Windows 2000 (also referred to as Win2K) is a preemptive, interruptible, graphical and business-oriented operating system that was designed to work with either uniprocessor or symmetric multi-processor 32-bit Intel x86 computers. ... Windows NT 4. ... Current logo of Winternals. ...

Windows 2000 and Windows XP can read and write to FAT32 filesystems of any size, but the format program on Windows XP can only create FAT32 filesystems up to 32 GiB. The format program with Windows 2000, however, can in fact create FAT32 filesystems larger than 32 Gib. Third party utilities are available which can format larger FAT32 filesystems, up to 2TB. Thompson and Thompson (2003) write^[8] that “Bizarrely, Microsoft states that this behavior is by design.” A Microsoft knowledge base article^[4] indeed confirms the limitation and the "by design" statement, but gives no rationale or explanation. However, a Microsoft TechNet article states that the 32 GB limit was an arbitrary limit imposed because many tasks on a very large FAT32 filesystem become slow and inefficient.^[9] Peter Norton's opinion^[10] is that “Microsoft has intentionally crippled the FAT32 file system.” Windows XP is a line of operating systems developed by Microsoft for use on general-purpose computer systems, including home and business desktops, notebook computers, and media centers. ... Peter Norton Peter Norton (born November 14, 1943) is an American software publisher and philanthropist. ...

The maximum possible size for a file on a FAT32 volume is 4 GB minus 1 Byte (2³²−1 bytes). For most users, this has become the most nagging limit of FAT32 as of 2007^{[citation needed]}, since video capture and editing applications and some other software can easily exceed this limit. Most new Windows machines now ship with NTFS and thus avoid these problems, but until mid-2006, those who run dual boot systems or who move external data drives between computers with different operating systems had little choice but to stick with FAT32. Since then, full support for NTFS has become available in Linux and many other operating systems, by installing the FUSE library (on Linux) together with the NTFS-3G application. Data exchange is also possible between Windows and Linux by using the Linux-native ext2 or ext3 file systems through the use of external drivers for Windows, such as ext2 IFS; however, Windows cannot boot from ext2 or ext3 partitions. Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, and Windows Vista. ... Filesystem in Userspace (FUSE) is a Free (GPL and LGPLed) Unix kernel module that allows non-privileged users to create their own file systems without the need to write any kernel code. ... NTFS-3G is an open source, freely available NTFS driver for Linux with read and write support. ... The ext2 or second extended file system is a file system for the Linux kernel. ... The ext3 or third extended filesystem is a journalled file system that is commonly used by the Linux operating system. ...

Fragmentation

The FAT filesystem does not contain mechanisms which prevent newly written files from becoming scattered across the partition.^[1] Other filesystems, like HPFS, use free space bitmaps that indicate used and available clusters, which could then be quickly looked up in order to find free contiguous areas (improved in exFAT). Another solution is the linkage of all free clusters into one or more lists (as is done in Unix filesystems). Instead, the FAT has to be scanned like an array in order to find free clusters, which can lead to performance penalties with today's large hard disks and consequently their large FAT sizes. exFAT (Extended File Allocation Table) is a file system suited especially for flash drives introduced with Windows CE 6. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ...

In fact, computing free disk space on FAT is one of the most resource intensive operations, as it requires reading the entire FAT linearly. A possible justification suggested by Microsoft's Raymond Chen for limiting the maximum size of FAT32 partitions created on Windows was the time required to perform a simple "DIR" operation, which always displays the free disk space as the last line.^[9] Displaying this line took longer and longer as the number of clusters increased. Raymond Chen is a well-known developer on the Windows Shell team at Microsoft. ...

The High Performance File System (HPFS) divides disk space into bands, which have their own free space bitmap, where multiple files opened for simultaneous write could be expanded separately.^[1]

Some of the perceived problems with fragmentation resulted from operating system and hardware limitations.

The single-tasking DOS and the traditionally single-tasking PC hard disk architecture (only 1 outstanding input/output request at a time, no DMA transfers) did not contain mechanisms which could alleviate fragmentation by asynchronously prefetching next data while the application was processing the previous chunks. Native Command Queuing (NCQ) is a technology designed to increase performance of SATA hard disks by allowing the individual hard disk to receive more than one I/O request at a time and dynamically change the order in which they are applied. ... The programmed input/output (PIO) interface was the original method used to transfer data between the CPU (through the ATA controller) and an ATA device. ...

Similarly, write-behind caching was often not enabled by default with Microsoft software (if present) given the problem of data loss in case of a crash, made easier by the lack of hardware protection between applications and the system.

MS-DOS also did not offer a system call which would allow applications to make sure a particular file has been completely written to disk in the presence of deferred writes (cf. fsync in Unix or DosBufReset in OS/2). Disk caches on MS-DOS were operating on disk block level and were not aware of higher-level structures of the file system. In this situation, cheating with regard to the real progress of a disk operation was most dangerous. sync is a standard system call in the Unix operating system, which commits to disk all data in the kernel filesystem buffers, i. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

Modern operating systems have introduced these optimizations to FAT partitions, but optimizations can still produce unwanted artifacts in case of a system crash. A Windows NT system will allocate space to files on FAT in advance, selecting large contiguous areas, but in case of a crash, files which were being appended will appear larger than they were ever written into, with dozens of random kilobytes at the end.

With the large cluster sizes, 16 or 32K, forced by larger FAT32 partitions, the external fragmentation becomes somewhat less significant, and internal fragmentation, ie. disk space waste (since files are rarely exact multiples of cluster size), starts to be a problem as well, especially when there are a great many small files.

Third party support

Other IBM PC operating systems—such as Linux, FreeBSD, BeOS and JNode—have all supported FAT, and most added support for VFAT, FAT32, JFAT shortly after the corresponding Windows versions were released. Early Linux distributions also supported a format known as UMSDOS, which was FAT with Unix file attributes (such as long file name and access permissions) stored in a separate file called “--linux-.---”. UMSDOS fell into disuse after VFAT was released and is not enabled by default in Linux kernels from version 2.5.7 onwards.^[11] The Mac OS X operating system also supports the FAT filesystems on volumes other than the boot disk. The Amiga supports FAT through the CrossDOS filesystem. This article is about operating systems that use the Linux kernel. ... FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ... BeOS is an operating system for personal computers which began development by Be Inc. ... JNode (Java New Operating System Design Effort) is an open-source project to create a Java platform operating system. ... UMSDOS is a filesystem driver for Linux that simulates the more advanced features of a UNIX filesystem while using an MS-DOS style FAT partition. ... The Linux kernel is a Unix-like operating system kernel. ... Mac OS X (IPA: ) is a line of graphical operating systems developed, marketed, and sold by Apple Inc. ... A boot disk is a removable media, normally read-only, that can boot an operating system or utility. ... The original Amiga 1000 (1985) with various peripherals The Amiga 500 (1987) was the most popular variant of the Amiga. ... CrossDOs was invented in 1986 by Arthur Brooney to Address the needs of higher performance users. ...

FAT and Alternate Data Streams

The FAT filesystem itself is not designed for supporting Alternate Data Streams (ADS), but some operating systems that heavily depend on them have devised various methods for handling them in FAT drives. Such methods either store the additional information in extra files and directories (Mac OS), or give new semantics to previously unused fields of the FAT on-disk data structures (OS/2 and Windows NT). The second design, while presumably more efficient, prevents any copying or backing-up of those volumes using non-aware tools; manipulating such volumes using non-aware disk utilities (e.g. defragmenters or CHKDSK) will probably lose the information. In computer file systems, a fork is additional data associated with a file system object. ... This article needs additional references or sources for verification. ...

Mac OS using PC Exchange stores its various dates, file attributes and long filenames in a hidden file called FINDER.DAT, and Resource Forks (a common Mac OS ADS) in a subdirectory called RESOURCE.FRK, in every directory where they are used. From PC Exchange 2.1 onwards, they store the Mac OS long filenames as standard FAT long filenames and convert FAT filenames longer than 31 characters to unique 31-character filenames, which can then be made visible to Macintosh applications. This article or section does not adequately cite its references or sources. ... PC Exchange was a Mac OS control panel that lets the operating system mount FAT file systems and mapped file extensions to the user-defined type and creator codes. ... There are very few or no other articles that link to this one. ...

Mac OS X stores metadata (Resource Forks, file attributes, other ADS) in a hidden file with a name constructed from the owner filename prefixed with "._", and Finder stores some folder and file metadata in a hidden file called ".DS_Store". Mac OS X (IPA: ) is a line of graphical operating systems developed, marketed, and sold by Apple Inc. ... .DS_Store (Desktop Services Store)[1] is a hidden file created by Apple Incs Mac OS X operating system to store custom attributes of a folder such as the position of icons or the choice of a background image[2]. By default, Mac OS X will create a . ...

OS/2 heavily depends on extended attributes (EAs) and stores them in a hidden file called "EA DATA. SF" in the root directory of the FAT12 or FAT16 volume. This file is indexed by 2 previously reserved bytes in the file's (or directory's) directory entry. In the FAT32 format, these bytes hold the upper 16 bits of the starting cluster number of the file or directory, hence making it difficult to store EAs on FAT32. Extended attributes are accessible via the Workplace Shell desktop, through REXX scripts, and many system GUI and command-line utilities (such as 4OS2).^[12] To meet Wikipedias quality standards, this article or section may require cleanup. ... Extended file attributes is a filesystem feature that enables users to associate arbitrary metadata with computer files, whereas regular attributes have a strictly defined purpose (such as permissions or records of creation and modification times). ... The OS/2 Warp 4 desktop (with some third-party enhancements installed as SOM classes) The Workplace Shell (WPS) is an award-winning object-oriented desktop shell produced by IBMs Boca Raton development lab for OS/2 2. ... REXX (REstructured eXtended eXecutor) is an interpreted programming language which was developed at IBM. It is a structured high-level programming language which was designed to be both easy to learn and easy to read. ... A graphical user interface (GUI) is a type of user interface which allows people to interact with a computer and computer-controlled devices which employ graphical icons, visual indicators or special graphical elements called widgets, along with text labels or text navigation to represent the information and actions available to... CLI is an acronym (or, strictly speaking, an initialism) for Command line interface Call Level Interface Common language interface (Commonly believed, but not official for Common Language Infrastructure) Common Language Infrastructure CLear Interrupts Composite Leading Indicator Caller Line Identification (telephony) Celebrity Love Island Critical Language Institute This page concerning a... 4DOS is a command line interpreter by JP Software originally designed to replace the DOS default command. ...

To accommodate its OS/2 subsystem, Windows NT supports the handling of extended attributes in HPFS, NTFS, and FAT. It stores EAs on FAT and HPFS using exactly the same scheme as OS/2, but does not support any other kind of ADS as held on NTFS volumes. Trying to copy a file with any ADS other than EAs from an NTFS volume to a FAT or HPFS volume gives a warning message with the names of the ADSs that will be lost. To meet Wikipedias quality standards, this article or section may require cleanup. ... Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... HPFS or High Performance File System is a file system created specifically for the OS/2 operating system to improve upon the limitations of the FAT file system. ... NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, and Windows Vista. ...

Windows 2000 onward acts exactly as Windows NT, except that it ignores EAs when copying to FAT32 without any warning (but shows the warning for other ADSs, like "Macintosh Finder Info" and "Macintosh Resource Fork"). Windows 2000 (also referred to as Win2K) is a preemptive, interruptible, graphical and business-oriented operating system that was designed to work with either uniprocessor or symmetric multi-processor 32-bit Intel x86 computers. ...

Future

Microsoft has recently secured patents for VFAT and FAT32 (but not the original FAT), which is causing concern that the company might later seek royalties from Linux distributions and from media vendors that pre-format their products (see FAT Licensing below). Despite two earlier rulings against them, Microsoft prevailed and was awarded the patents.

Since Microsoft has announced the discontinuation of its MS-DOS-based consumer operating systems with Windows Me, it remains unlikely that any new versions of FAT will appear. For most purposes, the NTFS file system that was developed for the Windows NT line is superior to FAT from the points of view of efficiency, performance, and reliability; its main drawbacks are the size overhead for small volumes and the very limited support by anything other than the NT-based versions of Windows, since the exact specification is a trade secret of Microsoft. The availability of NTFS-3G since mid 2006 has led to much improved NTFS support in Unix-like operating systems, considerably alleviating this concern. It is still not possible to use NTFS in DOS-like operating systems, which in turn makes it difficult to use a DOS floppy for recovery purposes. Microsoft provided a recovery console to work around this issue, but for security reasons it severely limited what could be done through the Recovery Console by default. The movement of recovery utilities to boot CDs based on BartPE or Linux (with NTFS-3G) is finally eroding this drawback. Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... Windows Millennium Edition, or Windows Me (IPA pronunciation: [miː], [ɛm iː]), is a hybrid 16-bit/32-bit graphical operating system released on September 14, 2000 by Microsoft. ... NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, and Windows Vista. ... A trade secret is a formula, practice, process, design, instrument, pattern, or compilation of information used by a business to obtain an advantage over competitors within the same industry or profession. ... NTFS-3G is an open source, freely available NTFS driver for Linux with read and write support. ... The Windows 2000 Recovery Console selection, login, and command prompts. ... BartPE is a Live CD version of the Microsoft Windows XP or Windows Server 2003 operating systems. ...

FAT is still the normal filesystem for removable media (with the exception of CDs and DVDs), with FAT12 used on floppies, and FAT16 on most other removable media (such as flash memory cards for digital cameras and USB flash drives). Most removable media are not yet large enough to benefit from FAT32, although some larger flash drives, like SDHC, do make use of it. FAT16 is used on these drives for reasons of compatibility and size overhead. A USB flash drive. ... A SiPix digital camera next to a matchbox to show scale Nikon D200 SLR with Nikon film scanner, which converts film images to digital A Hasselblad 503CW with a digital camera back A digital camera is an electronic device used to capture and store photographs digitally, instead of using photographic... Note: USB may also mean upper sideband in radio. ... A USB device for reading various kinds of flash memories, with an SD card plugged in Secure Digital (SD) is a flash (non-volatile) memory card format developed by Matsushita, SanDisk and Toshiba for use in portable devices, including digital cameras, handheld computers, PDAs and GPS units. ...

The FAT32 formatting support in Windows 2000 and XP is limited to volumes of 32 GB, which effectively forces users of modern hard drives either to use NTFS, to partition the drive into smaller volumes (below 32 GB), or to format the drive using third party tools. NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, and Windows Vista. ...

exFAT

Main article: exFAT

exFAT is an incompatible replacement for FAT filesystems that is expected to be introduced with Windows CE 6.0. It is intended to be used on flash drives, where FAT is used today. Windows XP and Vista file system drivers will be offered by Microsoft shortly after the release of Windows CE 6.0. exFAT introduces a free space bitmap allowing faster space allocation and faster deletes, support for files up to 2⁶⁴ bytes, larger cluster sizes (up to 32 MB in the first implementation), an extensible directory structure and name hashes for filenames for faster comparisons. It does not have short 8.3 filenames anymore. It does not appear to have security access control lists or file system journaling like NTFS, though device manufacturers can choose to implement simplified support for transactions (backup file allocation table used for the write operations, primary FAT for storing last known good allocation table). exFAT (Extended File Allocation Table) is a file system suited especially for flash drives introduced with Windows CE 6. ... Windows CE 6. ... A USB drive, shown with a 24 mm US quarter coin for scale. ... In computer security, an access control list (ACL) is a list of permissions attached to an object. ... A journaling (or journalling) file system is a file system that logs changes to a journal (usually a circular log in a specially-allocated area) before actually writing them to the main file system. ...

Design

The following is an overview of the order of structures in a FAT partition or disk:

A FAT file system is composed of four different sections.

1. The Reserved sectors, located at the very beginning. The first reserved sector is the Boot Sector (aka Partition Boot Record). It includes an area called the BIOS Parameter Block (with some basic file system information, in particular its type, and pointers to the location of the other sections) and usually contains the operating system's boot loader code. The total count of reserved sectors is indicated by a field inside the Boot Sector. Important information from the Boot Sector is accessible through an operating system structure called the Drive Parameter Block in DOS and OS/2. For FAT32 file systems, the reserved sectors include a Backup Boot Sector at Sector 6.
2. The FAT Region. This contains two copies of the File Allocation Table for the sake of redundancy, although the extra copy is rarely used, even by disk repair utilities. These are maps of the Data Region, indicating which clusters are used by files and directories.
3. The Root Directory Region. This is a Directory Table that stores information about the files and directories located in the root directory. It is only used with FAT12 and FAT16 and means that the root directory has a fixed maximum size which is pre-allocated at creation of this volume. FAT32 stores the root directory in the Data Region along with files and other directories instead, allowing it to grow without such a restraint.
4. The Data Region. This is where the actual file and directory data is stored and takes up most of the partition. The size of files and subdirectories can be increased arbitrarily (as long as there are free clusters) by simply adding more links to the file's chain in the FAT. Note however, that clusters are allocated in their entirety, and so if a 1 KB file resides in a 32 KB cluster, 31 KB are wasted.

FAT uses little endian format for entries in the header and the FAT(s). A boot sector is a sector of a hard disc, floppy disc, or similar data storage device that contains code for bootstrapping programs (usually, but not necessarily, operating systems) stored in other parts of the disc. ... BIOS parameter block (BPB) is a description of the physical medium (hard disk or floppy) that might be stored in a filesystems Volume Boot Record. ... In computing, endianness is the byte (and sometimes bit) ordering in memory used to represent some kind of data. ...

Boot Sector

Common structure of the first 36 bytes used by all FAT versions:

Further structure used by FAT12 and FAT16, also known as Extended BIOS Parameter Block:

The boot sector is portrayed here as found on e.g. an OS/2 1.3 boot diskette. Earlier versions used a shorter BIOS Parameter Block and their boot code would start earlier (for example at offset 0x2b in OS/2 1.1).

Further structure used by FAT32:

Exceptions

The implementation of FAT used in MS-DOS for the Apricot PC had a different boot sector layout, to accommodate that computer's non-IBM compatible BIOS. The jump instruction and OEM name were omitted, and the MS-DOS filesystem parameters (offsets 0x0B - 0x17 in the standard sector) were located at offset 0x50. Later versions of Apricot MS-DOS gained the ability to read and write disks with the standard boot sector in addition to those with the Apricot one. Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... The Apricot PC was Apricot Computers first personal computer made for business use. ... This article does not cite any references or sources. ...

DOS Plus on the BBC Master 512 did not use conventional boot sectors at all. Data disks omitted the boot sector and began with a single copy of the FAT (the first byte of the FAT was used to determine disk capacity) while boot disks began with a miniature ADFS filesystem containing the boot loader, followed by a single FAT. It could also access standard PC disks formatted to 180 KB or 360 KB, again using the first byte of the FAT to determine capacity. DOS Plus (also known as DOS+) is an operating system written by Digital Research, first released in 1985. ... A BBC Master 128 with monitor and disk drives. ... The Advanced Disc Filing System (ADFS) is a computing file system particular to the Acorn computer range and RISC OS based successors. ...

File Allocation Table

A partition is divided up into identically sized clusters, small blocks of contiguous space. Cluster sizes vary depending on the type of FAT file system being used and the size of the partition, typically cluster sizes lie somewhere between 2 KB and 32 KB. Each file may occupy one or more of these clusters depending on its size; thus, a file is represented by a chain of these clusters (referred to as a singly linked list). However these chains are not necessarily stored adjacent to one another on the disk's surface but are often instead fragmented throughout the Data Region. In computer science, a linked list is one of the fundamental data structures, and can be used to implement other data structures. ...

The File Allocation Table (FAT) is a list of entries that map to each cluster on the partition. Each entry records one of five things:

• the cluster number of the next cluster in a chain
• a special end of clusterchain (EOC) entry that indicates the end of a chain
• a special entry to mark a bad cluster
• a special entry to mark a reserved cluster^{[citation needed]}
• a zero to note that the cluster is unused

Each version of the FAT file system uses a different size for FAT entries. The size is indicated by the name, for example the FAT16 file system uses 16 bits for each entry while the FAT32 file system uses 32 bits. Only 28 of these are actually used, however. This difference means that the File Allocation Table of a FAT32 system can map a greater number of clusters than FAT16, allowing for larger partition sizes with FAT32. This also allows for more efficient use of space than FAT16, because on the same hard drive a FAT32 table can address smaller clusters which means less wasted space.

FAT entry values:

Note that FAT32 uses only 28 bits of the 32 possible bits. The upper 4 bits are usually zero but are reserved and should be left untouched. In the table above these are denoted by a question mark.

The first cluster of the data area is cluster #2. That leaves the first two entries of the FAT unused. In the first byte of the first entry a copy of the media descriptor is stored. The remaining 8 bits (if FAT16), or 20 bits (if Fat32) of this entry are 1. In the second entry the end-of-cluster-chain marker is stored. The high order two bits of the second entry are sometimes, in the case of FAT16 and FAT32, used for dirty volume management: high order bit 1: last shutdown was clean; next highest bit 1: during the previous mount no disk I/O errors were detected.^[16]

Directory table

A directory table is a special type of file that represents a directory (nowadays commonly known as a folder). Each file or directory stored within it is represented by a 32-byte entry in the table. Each entry records the name, extension, attributes (archive, directory, hidden, read-only, system and volume), the date and time of creation, the address of the first cluster of the file/directory's data and finally the size of the file/directory. Aside from the Root Directory Table in FAT12 and FAT16 file systems which occupies the special Root Directory Region location, all Directory Tables are stored in the Data Region. The actual number of entries in a directory stored in the Data Region can grow by adding another cluster to the chain in the FAT. An archive bit is a file attribute present in many computer file systems, notably FAT, FAT32, and NTFS. The purpose of an archive bit is to track incremental changes to files for the purpose of backup (also called archiving). ...

Legal characters for DOS file names include the following:

• Upper case letters A–Z
• Numbers 0–9
• Space (though trailing spaces in either the base name or the extension are considered to be padding and not a part of the file name, also filenames with space in could not be used on the DOS command line because of the lack of a suitable escaping system)
• ! # $ % & ' ( ) - @ ^ _ ` { } ~
• (FAT-32 only) + , . ; = [ ]
• Values 128–255

This excludes the following ASCII characters: Image:ASCII fullsvg There are 95 printable ASCII characters, numbered 32 to 126. ...

• " * / : < > ? |
  Windows/MSDOS has no shell escape character
• Lower case letters a–z
  stored as A–Z on FAT-12/16
• Control characters 0–31
• Value 127 (DEL)

The DOS file names are in the OEM character set. In computing and telecommunication, an escape character is one which has a special meaning in a sequence of characters. ... Code page is the traditional IBM term used for a specific character encoding table: a mapping in which a sequence of bits, usually a single octet representing integer values 0 through 255, is associated with a specific character. ...

Directory entries, both in the Root Directory Region and in subdirectories, are of the following format:

To meet Wikipedias quality standards, this article or section may require cleanup. ...

Long file names

Long File Names (LFN) are stored on a FAT file system using a trick—adding phony entries into the Directory Tables. The entries are marked with a Volume Label attribute which is impossible for a regular file and because of that they are ignored by most old MS-DOS programs. Notably, a directory containing only volume labels is considered as empty and is allowed to be deleted; such a situation appears if files created with long names are deleted from plain DOS.

A checksum also allows verification of whether a long file name matches the 8.3 name; such a mismatch could occur if a file was deleted and re-created using DOS in the same directory position. The checksum is calculated using the algorithm below. (Note that pFcbName is a pointer to the name as it appears in a regular directory entry, i.e. the first eight characters are the filename, and the last three are the extension. The dot is implicit. Any unused space in the filename is padded with spaces (ASCII 0x20) char. For example, "Readme.txt" would be "README  TXT".) A checksum is a form of redundancy check, a simple way to protect the integrity of data by detecting errors in data that are sent through space (telecommunications) or time (storage). ...

 unsigned char lfn_checksum(const unsigned char *pFcbName) { int i; unsigned char sum=0; for (i=11; i; i--) sum = ((sum & 1) << 7) + (sum >> 1) + *pFcbName++; //sum = ((sum & 1) ? 0x80 : 0) + (sum >> 1) + *pFcbName++; return sum; } 

Older versions of PC-DOS mistake LFN names in the root directory for the volume label, and are likely to display an incorrect label.

Each phony entry can contain up to 13 UTF-16 characters (26 bytes) by using fields in the record which contain file size or time stamps (but not the starting cluster field, for compatibility with disk utilities, the starting cluster field is set to a value of 0). See 8.3 filename for additional explanations. Up to 20 of these 13-character entries may be chained, supporting a maximum length of 255 UTF-16 characters.^[17] In computing, UTF-16 is a 16-bit Unicode Transformation Format, a character encoding form that provides a way to represent a series of abstract characters from Unicode and ISO/IEC 10646 as a series of 16-bit words suitable for storage or transmission via data networks. ... A 8. ...

LFN entries use the following format:

If a filename contains only lowercase letters, or is a combination of a lowercase basename with an uppercase extension, or vice-versa; and has no special characters, and fits within the 8.3 limits, a VFAT entry is not created on Windows NT and later versions such as XP. Instead, two bits in byte 0x0c of the directory entry are used to indicate that the filename should be considered as entirely or partially lowercase. Specifically, bit 4 means lowercase extension and bit 3 lowercase basename, which allows for combinations such as "example.TXT" or "HELLO.txt" but not "Mixed.txt". Few other operating systems support this. This creates a backwards-compatibility problem with older Windows versions (95, 98, ME) that see all-uppercase filenames if this extension has been used, and therefore can change the name of a file when it is transported, such as on a USB flash drive. Current 2.6.x versions of Linux will recognize this extension when reading (source: kernel 2.6.18 /fs/fat/dir.c and fs/vfat/namei.c); the mount option shortname determines whether this feature is used when writing.^[18] In computing, UTF-16 is a 16-bit Unicode Transformation Format, a character encoding form that provides a way to represent a series of abstract characters from Unicode and ISO/IEC 10646 as a series of 16-bit words suitable for storage or transmission via data networks. ... In computing, UTF-16 is a 16-bit Unicode Transformation Format, a character encoding form that provides a way to represent a series of abstract characters from Unicode and ISO/IEC 10646 as a series of 16-bit words suitable for storage or transmission via data networks. ... In computing, UTF-16 is a 16-bit Unicode Transformation Format, a character encoding form that provides a way to represent a series of abstract characters from Unicode and ISO/IEC 10646 as a series of 16-bit words suitable for storage or transmission via data networks. ...

Third-party extensions

Before Microsoft added support for long filenames and creation/access time stamps, bytes 0x0C–0x15 of the directory entry were used by alternative operating systems to store additional metadata. These included:

This article does not cite any references or sources. ... DOS Plus (also known as DOS+) is an operating system written by Digital Research, first released in 1985. ... This article does not cite any references or sources. ...

FAT licensing

Microsoft applied for, and was granted, a series of patents for key parts of the FAT file system in the mid-1990s. Being almost universally compatible and well-understood, FAT is frequently chosen as an interchange format for flash media used in digital cameras and PDAs. Flash memory is a form of EEPROM that allows multiple memory locations to be erased or written in one programming operation. ... A SiPix digital camera next to a matchbox to show scale Nikon D200 SLR with Nikon film scanner, which converts film images to digital A Hasselblad 503CW with a digital camera back A digital camera is an electronic device used to capture and store photographs digitally, instead of using photographic... User with PDA Personal digital assistants (PDAs) are handheld computers that were originally designed as personal organizers, but became much more versatile over the years. ...

On 2003-12-03 Microsoft announced it would be offering licenses for use of its FAT specification and "associated intellectual property", at the cost of a US$0.25 royalty per unit sold, with a $250,000 maximum royalty per license agreement.^[19] Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... is the 337th day of the year (338th in leap years) in the Gregorian calendar. ...

To this end, Microsoft cited four patents on the FAT filesystem as the basis of its intellectual property claims. All four pertain to long-filename extensions to FAT first seen in Windows 95: Windows 95 is a consumer-oriented graphical user interface-based operating system. ...

• U.S. Patent 5,745,902  - Method and system for accessing a file using file names having different file name formats. Filed July 6, 1992. This covered a means of generating and associating a short, 8.3 filename with long one (for example, "Microsoft.txt" with "MICROS~1.TXT") and a means of enumerating conflicting short filenames (for example, "MICROS~2.TXT" and "MICROS~3.TXT"). It is unclear whether this patent would cover an implementation of FAT without explicit long filename capabilities. Hard links in Unix file systems do not appear to be prior art: deleting a FAT file via its long name will also remove its short name. Renaming a file to a "short" name also updates the long file name for coherency; similarly, renaming a file to a "long" name will allocate a new "short" name. In NTFS, hard links and dual names are separate concepts and each hard link has two names. Finally, at the API level, both names are always provided together when a directory lookup is requested from the system; they do not appear as two separate files and do not have to be "matched" to determine unique files.
• U.S. Patent 5,579,517  - Common name space for long and short filenames. Filed for on 1995-04-24. This covers the method of chaining together multiple consecutive 8.3 named directory entries to hold long filenames, with some of the entries specially marked to prevent their confusing older, long filename-unaware FAT implementations.
  • The Public Patent Foundation successfully challenged this patent; the claims were rejected^[20] on 2004-09-14, due to prior disclosure^[21] of the claimed techniques in patents U.S. Patent 5,307,494  and U.S. Patent 5,367,671 . This decision was later overturned by the Patent Office on 2006-01-10.
• U.S. Patent 5,758,352  - Common name space for long and short filenames. Filed on 1996-09-05. This is very similar to 5,579,517.
  • The Public Patent Foundation successfully challenged this patent; The USPTO rejected this patent on 2005-10-05, on the grounds that "the six assignees names were incorrect".^[22][23] This decision was also later overturned by the Patent Office on 2006-01-10.
• U.S. Patent 6,286,013  - Method and system for providing a common name space for long and short file names in an operating system. Filed on 1997-01-28. This makes claims on the methods used when Windows 95, Windows 98 and Windows Me expose long filenames to their MS-DOS compatibility layer. It does not appear to affect any non-Microsoft FAT implementations.

Many technical commentators have concluded that these patents only cover FAT implementations that include support for long filenames, and that removable solid state media and consumer devices only using short names would be unaffected. is the 187th day of the year (188th in leap years) in the Gregorian calendar. ... Year 1992 (MCMXCII) was a leap year starting on Wednesday (link will display full 1992 Gregorian calendar). ... A 8. ... In computing, a hard link is a reference, or pointer, to physical data on a storage volume. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... This article or section cites very few or no references or sources. ... Year 1995 (MCMXCV) was a common year starting on Sunday (link will display full 1995 Gregorian calendar). ... is the 114th day of the year (115th in leap years) in the Gregorian calendar. ... A 8. ... Public Patent Foundation, or PUBPAT, is a nonprofit organization that seeks to limit perceived abuse of the U.S. Patent system. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 257th day of the year (258th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 10th day of the year in the Gregorian calendar. ... Year 1996 (MCMXCVI) was a leap year starting on Monday (link will display full 1996 Gregorian calendar). ... is the 248th day of the year (249th in leap years) in the Gregorian calendar. ... Public Patent Foundation, or PUBPAT, is a nonprofit organization that seeks to limit perceived abuse of the U.S. Patent system. ... The United States Patent and Trademark Office (PTO or USPTO) is an agency in the United States Department of Commerce that provides patent and trademark protection to inventors and businesses for their inventions and corporate and product identification. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 278th day of the year (279th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 10th day of the year in the Gregorian calendar. ... For the band, see 1997 (band). ... is the 28th day of the year in the Gregorian calendar. ... Windows 95 is a consumer-oriented graphical user interface-based operating system. ... Windows 98 (codenamed Memphis and formerly known as Windows 97[2]) is a graphical operating system released on June 25, 1998 by Microsoft and the successor to Windows 95. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ...

Additionally, in the document "Microsoft Extensible Firmware Initiative FAT 32 File System Specification, FAT: General Overview of On-Disk Format" published by Microsoft (version 1.03, 2000-12-06), Microsoft specifically grants a number of rights, which many readers have interpreted as permitting operating system vendors to implement FAT. Year 2000 (MM) was a leap year starting on Saturday (link will display full 2000 Gregorian calendar). ... December 6 is the 340th day of the year (341st in leap years) in the Gregorian calendar. ...

Microsoft is not the only company to have applied for patents for parts of the FAT file system. Other patents affecting FAT include:

• U.S. Patent 5,367,671  - System for accessing extended object attribute (EA) data through file name or EA handle linkages in path tables. Filed on 1990-09-25 by Barry A. Feigenbaum and Felix Miro of IBM, this makes claims on the methods used by OS/2, Windows NT, and Linux for storing extended attribute data in the "EA DATA. SF" file.

Year 1990 (MCMXC) was a common year starting on Monday (link displays the 1990 Gregorian calendar). ... is the 268th day of the year (269th in leap years) in the Gregorian calendar. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... This article is about operating systems that use the Linux kernel. ...

Appeal

As there was widespread call for these patents to be re-examined, the Public Patent Foundation (PUBPAT) submitted evidence to the US Patent and Trade Office (USPTO) disputing the validity of these patents, including prior art references from Xerox and IBM. The USPTO acknowledged that the evidence raised "substantial new question[s] of patentability," and opened an investigation into the validity of Microsoft's FAT patents.^[24] Public Patent Foundation, or PUBPAT, is a nonprofit organization that seeks to limit perceived abuse of the U.S. Patent system. ... The United States Patent and Trademark Office (PTO or USPTO) is an agency in the United States Department of Commerce that provides patent and trademark protection to inventors and businesses for their inventions and corporate and product identification. ... Xerox Corporation (NYSE: XRX) (name pronounced ) is a global document management company, which manufactures and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies. ... For other uses, see IBM (disambiguation) and Big Blue. ...

On 2004-09-30 the USPTO rejected all claims of U.S. Patent 5,579,517 , based primarily on evidence provided by PUBPAT. Dan Ravicher, the foundation's executive director, said, "The Patent Office has simply confirmed what we already knew for some time now, Microsoft's FAT patent is bogus." Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 273rd day of the year (274th in leap years) in the Gregorian calendar. ...

According to the PUBPAT press release, "Microsoft still has the opportunity to respond to the Patent Office's rejection. Typically, third party requests for reexamination, like the one filed by PUBPAT, are successful in having the subject patent either narrowed or completely revoked roughly 70% of the time."

On 2005-10-05 the Patent Office announced that, following the re-examination process, it had again rejected all claims of patent 5,579,517, and it additionally found U.S. Patent 5,758,352  invalid on the grounds that the patent had incorrect assignees. Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 278th day of the year (279th in leap years) in the Gregorian calendar. ...

Finally, on 2006-01-10 the Patent Office ruled that features of Microsoft's implementation of the FAT system were "novel and non-obvious", reversing both earlier non-final decisions.^[25] Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 10th day of the year in the Gregorian calendar. ...

See also

• Comparison of file systems
• Drive letter assignment
• FreeDOS has full FAT support
• Software patent
• List of file systems
• Rock Ridge and Joliet — systems for CDs that add long file names similar to what VFAT did for FAT.

This article does not cite any references or sources. ... Drive letter assignment is the process of assigning drive letters to primary and logical partitions (drive volumes) in the root namespace; this usage is found in Microsoft operating systems. ... FreeDOS (formerly Free-DOS and PD-DOS) is an operating system for IBM PC compatible computers. ... Software patent does not have a universally accepted definition. ... The following lists identify, characterise and link to more thorough information on computer file systems. ... The Rock Ridge Interchange Protocol (RRIP, IEEE P1282) is an extension to the ISO 9660 volume format which adds POSIX file system semantics. ... Joliet is the name of an extension to the ISO 9660 file system. ...

References

Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 67th day of the year (68th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 24th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 8 is the 98th day of the year (99th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 72nd day of the year (73rd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 287th day of the year (288th in leap years) in the Gregorian calendar. ...

External links

• ECMA-107 Volume and File Structure of Disk Cartridges for Information Interchange, identical to ISO/IEC 9293.
• Microsoft Extensible Firmware Initiative FAT 32 File System Specification, FAT: General Overview of On-Disk Format
• Understanding FAT32 Filesystems (explained for embedded firmware developers)
• Detailed Explanation of FAT Boot Sector - Microsoft Knowledge Base Article 140418
• Volume and file size limits of FAT filesystems
• Microsoft TechNet: A Brief and Incomplete History of FAT32 by Raymond Chen
• FAT 32 Formatter: allows formatting volumes larger than 32GB with FAT32 under Windows 2000, Windows XP and Windows Vista
• Fdisk Does Not Recognize Full Size of Hard Disks Larger than 64 GB - Microsoft Knowledge Base Article 263044.
• Microsoft Windows XP - FAT32 File System - Copy made by Internet Archive Wayback Machine of an article with summary of limits in FAT32 which is not longer available on Microsoft website.
• EFSL, Open source FAT implementation for embedded devices

Raymond Chen is a well-known developer on the Windows Shell team at Microsoft. ... Windows 2000 (also referred to as Win2K) is a preemptive, interruptible, graphical and business-oriented operating system that was designed to work with either uniprocessor or symmetric multi-processor 32-bit Intel x86 computers. ... Windows XP is a line of operating systems developed by Microsoft for use on general-purpose computer systems, including home and business desktops, notebook computers, and media centers. ... Windows Vista is a line of graphical operating systems used on personal computers, including home and business desktops, notebook computers, Tablet PCs, and media centers. ...