What Does MS-DOS FAT Mean?

Updated March 27, 2017

In the world of computers, there can be too many acronyms to keep up with. One of the more common ones that you might run into is "MS-DOS FAT." Though not as popular as they used to be, the MS-DOS operating system and FAT disk format can still be found in use as of July 2011. Their origin goes long back to the early days of personal computing, when companies such as Microsoft and Apple were in their infancy.


MS-DOS is an early Microsoft-created operating system. It gets its name from its longer name, which is Microsoft Disk Operating System. Unlike more-modern operating systems, MS-DOS did not offer a graphical interface and instead was managed by typing commands into a text prompt on the screen. MS-DOS was first developed and released in 1981, seeing its final release in 1994, after graphical user interfaces had gained more prominence.


FAT is a type of file system management that was employed by the MS-DOS operating system. Short for File Allocation Table, FAT was the method by which MS-DOS kept a record of its hard drive contents, such as what files and program files were installed on the computer. FAT was popular when it was first developed, but became eclipsed by more-efficient disk management systems, one of which is known as NTFS, which is still used with Microsoft operating systems as of July 2011.

FAT Versions

Over the years, there were three main versions of FAT developed and used by MS-DOS and early graphic Microsoft operating systems. The first version was FAT12, which used a 12-bit binary system to management disk files. The second iteration was FAT16, which functioned like FAT12, but used a 16-bit binary system. Both FAT12 and FAT16 hit their obsolescence when FAT32 was introduced, which uses a 28-bit binary system that helps free up more disk space than the previous versions.


While the FAT management platform was used through the late 1990s, its compatibility with MS-DOS is limited to FAT12 and FAT16. The FAT32 disk management system was released with Windows 95. However, the earlier FAT12 and FAT16 systems remained compatible with MS-DOS as well as Windows 95, allowing users of older machines to upgrade to new disk management without having to purchase and install a fresh operating system.

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About the Author

Peter Grant has been a professional writer since 1998 and software engineer since 1995. He has contributed to academic papers, open-source software projects and technical documentation across several industries. Grant holds a master's degree in public policy from National University.