The very first operating system used on the earliest IBM PCs was called simply the Disk Operating System, abbreviated DOS. There are few PC users who have not heard of DOS; at one time it was used on pretty much every PC, and it is still around today in many different forms. Microsoft's version of DOS is the most common one, and is called MS-DOS--with the "MS" abbreviation being rather self-explanatory. :^) For a while IBM Corporation was producing a competing product called PC-DOS, and there are other companies' alternatives around as well.

As the name "DOS" implies, the use of disks is an inherent part of the DOS operating system. The FAT file system has been an essential component of DOS since the beginning, and generally speaking, DOS uses only various versions of FAT for managing files.

The most confusion is caused by the "appearance" of FAT32 support in the second release of Windows 95--corresponding to DOS 7.1--which was complicated by the fact that later versions of Windows that support FAT32 were not "officially" sold to the public. See the discussions of Windows 95A and Windows 95B and 95C for more information.

The most confusion is caused by the "appearance" of FAT32 support in the second release of Windows 95--corresponding to DOS 7.1--which was complicated by the fact that later versions of Windows that support FAT32 were not "officially" sold to the public. See the discussions of Windows 95A and Windows 95B and 95C for more information.

Microsoft's first foray into the world of the graphical operating system was Microsoft Windows 1.0. I never used this product, but it is universally considered to have been rather scary. :^) Bill Gates and company did not give up, and subsequent versions of Windows followed. Microsoft finally started to pick up a head of steam with the release of Windows 3.0. The versions that followed, including Windows 3.1, Windows 3.11 and Windows for Workgroups 3.11, were the most common graphical operating systems used in the early 1990s, prior to the creation of Windows 95. These are often collectively called Windows 3.x.

To the technical purist, Windows 3.x isn't a true "operating system". The reason is that it runs strictly on top of DOS, and uses DOS (and BIOS) facilities and routines for most of its hardware management, including disk access. For this reason, some consider it just a "graphical shell". Another famous "Bill" made the point that names don't matter all that much, but for our purposes, the matter of what Windows 3.x really is does matter. Since it uses DOS for disk access, this means that Windows has the same file system support as whatever version of DOS underlies it. In most cases that is MS-DOS 6.x, most commonly MS-DOS 6.22. See this discussion of DOS file system support for more information.

The last version of Windows 3.x, Windows for Workgroups 3.11, includes an enhancement called "32-Bit File Access". This is really a poorly-named feature that refers to the use of 32-bit protected mode routines for accessing the disk, instead of using the standard 16-bit DOS routines. In fact, this is really the first, partial implementation of the VFAT file system used by Windows 95, although not all of the VFAT features are included--only the use of 32-bit access routines. The only thing different here is how the disk is accessed; the file system structures are still "plain" FAT, so special features like long filenames are not included.