FAT16

The 16-bit version of the File Allocation Table (FAT) file systemhereafter FAT16was first used with DOS back when I was in parachute pants (that would be 1981). FAT16 divides the space on a fixed disk into 65,536 (which is 16 bits' worth, or 2¹⁶) storage locations, and each location is assigned a number. The storage locations are also known as clusters. A cluster is the smallest unit of storage space on a FAT partition. A cluster can be allocated for a single file only, even if the file does not use up all the storage space. Also, a cluster can store just a part of a larger file.

The location of files in these storage spaces is tracked by the File Allocation Table, which, as mentioned, works similarly to the table of contents for this book. The File Allocation Table says, "File x is stored in the location starting with the number 11, and it uses storage boxes 12-18, skips a few, uses 23-25, and the rest is in boxes 59-67. (Such a file would be fragmented, a condition we'll address in a later chunk.) The read/write heads of the hard disk know exactly where to travel to quickly find and retrieve the requested data from storage locations 11 through 67. (Of course, not all data from these storage boxes will be retrieved, just the ones the File Allocation Table has designated as locations for file x.)

The main advantage of FAT is that almost all operating systems support it. This can be an important consideration if you want to dual boot with other operating systems.

It is also a good choice for small partitions (500MB or less), which operate with better performance when using FAT16 instead of NTFS. The storage "overhead" associated with FAT partitions in general is much smaller than with NTFS.

The FAT16 file system has two significant drawbacks, however, because it was designed when software was distributed onget thisfloppy disks. It was designed to be a single-user file system and does not support any kind of local security. In addition, the maximum partition size is limited to 4GB. As you know, you can now strap 4GB of storage around your wrist.