Answer： Generally speaking, there are three formats of USB flash drives, which are produced because of their different needs. FAT, FAT32, exFAT. Early U disk capacity was small. It is in FAT16 format. Referred to as FAT format. Now USB flash drives of 2GB and below are in this format. As the file size becomes larger, some individual files exceed 2GB in size. The FAT format of this type of file is not support ed, so the FAT32 format appears. Now 4GB-32GB U disks are in this format; Subsequently, a single file with a size of more than 4GB appeared. This type of file FAT32 format is not supported. So the FAT64 format, or exFAT for short, appeared. Now 64G and above U disks are in this format; A small-capacity USB flash drive can be made into a large format, such as 16GB can also be made into an exFAT format, which will not have a significant impact on the use of the USB flash drive. This solution can be used to store a single file of more than 4GB. Conversely, a large-capacity U disk can also be made into a small format, but when the file size exceeds the standard, the corresponding file cannot be stored. In addition, U disk can be made into NTFS hard disk format and CDFS disc format when encountering some special situations.