FAT is File Allocation Table (English: File Allocation Table, acronym: FAT). It is a file system invented and partially patented by Microsoft for use by MS-DOS and all non- The file system used by the NT core of Microsoft Windows. The FAT file system was not complicated considering the limited computer performance at the time, so it is supported by almost all personal computer operating systems. This feature makes it an ideal floppy disk and memory card file system, and also suitable for data exchange between different operating systems. Now, generally speaking, FAT refers specifically to FAT32. However, FAT has a serious shortcoming: when a file is deleted and new data is written, FAT will not organize the file into complete fragments before writing. After long-term use, the file data will gradually become scattered, which will slow down the reading and writing speed. Defragmentation is one solution, but frequent defragmentation is necessary to keep the FAT file system efficient.