The DOS filesystem provides transparent access to DOS disks, so you can treat DOS filesystems as though they were QNX Neutrino (POSIX) filesystems. This transparency lets processes operate on DOS files without any special knowledge or work on their part.
The fs-dos.so shared object (see the Utilities Reference) lets you mount DOS filesystems (FAT12, FAT16, and FAT32) under QNX Neutrino. This shared object is automatically loaded by the devb-* drivers when mounting a DOS FAT filesystem.
For information about valid characters for filenames in a DOS filesystem, see the Microsoft Developer Network at http://msdn.microsoft.com. FAT 8.3 names are the most limited; they're uppercase letters, digits, and $%'-_@{}~#(). VFAT names relax it a bit and add the lowercase letters and [];,=+. The QNX Neutrino DOS filesystem silently converts FAT 8.3 filenames to uppercase, to give the illusion that lowercase is allowed (but it doesn't preserve the case).
For more information on the DOS filesystem manager, see fs-dos.so in the Utilities Reference and Filesystems in the System Architecture guide.