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.
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).
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.
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; the filesystem was the main difference between 86-DOS and its predecessor, CP/M.
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.
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).
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.
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; the filesystem was the main difference between 86-DOS and its predecessor, CP/M.
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.
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