Electronic devices and operation methods of a file system

An electronic device, comprising:

• a random access memory coupled to a bus for storing temporary data;
• a flash memory coupled to the bus for storing a location information;
• a processor coupled to the bus for retrieving a first header of a first file and a file allocation table from a memory card, writing the first header and the file allocation table into the random access memory, wherein the first file comprises the first header and a data segment, the data segment comprises a first data segment and a second data segment, a plurality of clusters A1˜AN chained together constitute the first file, each of the clusters A1˜AN has a first data length, a data length of the first data segment is smaller than the first data length, the first header and the first data segment are stored in the clusters A1˜AY, the second data segment is stored in the clusters AY+1AN, N and Y are positive integer, and N>Y, the first data segment is stored in the cluster AY;
• wherein the processor further retrieves the location information and writes it into the first header to generate a second header, writes dummy data into the second header to adjust the data length of the second header, thereby serving as a third header, and modifies a link relation of clusters recorded in the file allocation table such that the third header and the second data segment are linked together, thereby generating a second file.