3.1 to run. On x86 computers, the virtual DOS machine uses the virtual 8086 mode to run DOS applications directly, on RISC computers, an emulator licensed from Insignia Solutions is used which emulates a 80286 processor. However, not all DOS and 16-bit Windows applications can be run on Windows NT 3.1 due to various limitations, one of them being the inability of applications to directly access the hardware. As well, VxD files sometimes needed by applications cannot be used with Windows NT 3.1. While pure DOS applications are run in separate memory spaces, 16-bit Windows applications have to share one memory space. While this is done due to compatibility reasons with applications which depend on this ability, like Schedule+ and Microsoft Mail, it also means that 16-bit Windows applications only run in cooperative multitasking. A faulty 16-bit Windows application is in this way able to cause all other 16-bit Windows applications (but not Windows NT itself) to crash. System Windows NT 3.1 provides a boot manager called NTLDR which is loaded during the startup process of the operating system on x86-based computers. It allows a multiboot setup of multiple instances of Windows NT 3.1, as well as MS-DOS and OS/2 1.x. NTLDR is not used for the RISC versions because the RISC computers' firmware provides their own boot manager. Every user has to log on to the computer after Windows NT 3.1 is booted up by pressing the key combination Ctrl+Alt+Del and entering the user name and password. All users have their own user account, and user-specific settings like the Program Manager groups are stored separately for every user. Users can be assigned specific rights, like the right to change the system time or the right to shut down the computer. To facilitate management of user accounts, it is also possible to group multiple user accounts and assign rights to groups of users. Windows NT 3.1 introduced the new NTFS file system. This new file system is more robust against hardware failures and allows assignment of read and write rights to users or groups on the file system level. NTFS supports long file names and has features to accommodate POSIX applications like hard links. For compatibility reasons, Windows NT 3.1 also supports FAT16 as well as OS/2's file system HPFS, but does not support long file names on FAT file system (VFAT). This was added in Windows NT 3.5. Designed