Disk File Systems

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I recommend you read The Right Order section before continuing

In order to understand this section on formatting, read the Boot Disks and Partition Theory menu items first. A disk must be partitioned before it can be formatted. Careful understanding and planning is important before any of these processes can be undertaken.

The way that information is stored on a disk is recorded in the disk's File Allocation Table (FAT) in DOS and DOS-based versions of Windows. This table is not normally user viewable, but it contains records of files, file sizes and other file details. It is what tells Windows Explorer how to display the contents of any given disk. It is the process of formatting which decides the FAT which will be used.

There are a few different types of file system, each with slightly different features. You need to know which type of FAT is appropriate to your needs and to the operating system you're planning to use. The last version of pure DOS was 6.22 and this came with a FAT called FAT16 (originally just known as FAT).

FAT16 (RIP)

Fat16 was not very efficient when it comes to larger partitions and tended to waste a lot of space in the way it stored files. The larger the partition, the more space wastage. In fact, FAT16 cannot recognise partition sizes above 2.1GB and so is only suitable for smaller disks and/or smaller partitions. Fat16's main advantage was that it used to be pretty universal amongst all the versions of File Allocation Tables and all the other Microsoft operating system FATs could 'see' it. More on this later.

FAT32 (now, mostly used on USB thumb drives

Windows 95b introduced FAT32 which was much more efficient and did not waste file space as much as FAT16. In addition, FAT32 was less prone to fragmentation. FAT32 can recognise very large partition sizes and was the FAT of choice with Windows 95b onwards.

A FAT32 hard disk partition cannot be read by a floppy which has been sys-ed from DOS 6.22, however, so it's important to use the Windows 95b or later version of DOS (sometimes referred to as DOS 7) to sys the boot floppy diskette. This will allow it to read both FAT and FAT32 hard disk partitions. FAT32 Supports disk/partitions up to 2 terabytes (2000 gigabytes), but only supports file sizes up to 4GB when running under DOS-based Windows.

NTFS

Windows NT 4.0 introduced a file system called NTFS (New Technology File System). NTFS has many benefits including security, fault tolerance, compression and better large partition performance. An NTFS partition cannot be read from a FAT16 or FAT32 partition. For instance if a PC was set up with two primary partitions, one FAT32 and one NTFS, to boot to either Win98 or WinNT respectively, neither OS would be able to see the other's partition. However they would both be able to see a separate logical drive if it was FAT16 formatted.

The maximum partition size for NTFS is 16 exabytes (1 exabyte=1 billion gigabytes). You could actually install WinNT on a FAT16 partition if you didn't need the security or large partition support features, which is a scary thought..

HPFS

The relatively obscure Microsoft/IBM OS2 operating system of a few years ago used a file system called HPFS (High Performance File System). This is no longer supported by WinNT and cannot be read from any of the other file systems, but could read FAT16 partitions.

NTFS5

Windows 2000 (and later) were originally based on Windows NT, with some borrowed Win98 features. Win2K brought a new file system called NTFS5. This new file system offers even higher security than NTFS, with additional features such as inbuilt encryption. An added bonus of Win2k is that it could read FAT16, FAT32 and NTFS partitions and can even be installed on a FAT32 partition if security was not an issue (which it should be).

These are the file systems used by Microsoft operating systems. Operating systems such as Linux, Unix and Apple OSX use their own types of file systems such as EXT3 and EXT4.