Summary of FAT file system 3
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Seven, FAT table structure FAT table (File Alloacation Table) is the number of clusters in the data correspond to the list.File system allocates disk space allocated by cluster. Thus, when the file occupies disk space, but the basic unit is not byte clusters, even if only one byte of a file, the operating system will assign it a minimum unit: that a cluster. For orderly disk space can be allocated to the appropriate file, read the file when they can read files from the corresponding address, we can put the data area space into BPB_BytsPerSec * BPB_SecPerClus-byte clusters to manage, FAT table Type Size and FAT table entries related, FAT12 entries is 12bit, FAT16 is 16bit, and FAT32 was 32bit.For large files, you need to assign multiple clusters. Data is not necessarily the same file stored on disk in a complete one continuous area region, and often will be divided into several sections, the same as the chain store. This storage is called a chain store files. In order to achieve the chain store files, the file system must accurately record which has been occupied cluster file, you must also specify the storage space of the next successor for each cluster in the cluster has been occupied for the last cluster of the file, No successor will have to specify the cluster cluster. These are the FAT table to hold the corresponding entries in the FAT table records the information it represents clusters: such is empty, is not a bad cluster, if it is already the end of the cluster, such as a file.
An example to FAT16 FAT is structured as follows:
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