Windows NT Subsystems and Associated Files

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1

The following information describes the files associated with each subsystem in Windows NT and the files associated with the virtual MS-DOS machine (VDM) and the Windows on Windows (WOW) environment.

WIN32 Subsystem

CSRSS.EXE    - Main component of Win32 subsystem.

GDI32.DLL    - *
USER32.DLL   - *

 * These files are 32-bit equivalents of the similarly-named Windows
   files.

POSIX Subsystem

PSXSS.EXE    - Main component of POSIX subsystem.
PSXDLL.DLL   - Handles communication between applications and
               PSXSS.EXE.
POSIX.EXE    - Handles communications between POSIX and the Windows NT
               executive.

OS/2 Subsystem

OS2SS.EXE    - Main component of OS/2 subsystem.
OS2DLL.DLL   - Handles communication between OS/2 application and
               subsystem.
OS2.EXE      - Passes name and command line parameters to OS2SVR.EXE.
OS2SRV.EXE   - Component that starts the application for the subsystem.

MS-DOS Virtual DOS Machine (VDM)

NTIO.SYS     - The equivalent of IO.SYS on MS-DOS machines.
NTDOS.SYS    - The equivalent of MSDOS.SYS.
NTVDM.EXE    - Win32 Application.
NTVDM.DLL    - Win32 Application.
REDIR.EXE    - Virtual Device Driver (VDD) redirector for the VDM.

Window on Windows (WOW)

WOWEXEC.EXE - Handles the loading of 16-bit Windows-based applications.

WOW32.DLL    - Dynamic Link Library of the WOW application environment.
NTVDM.EXE    - VDM Component.
NTVDM.DLL    - VDM Component.
NTIO.SYS     - VDM Component.
REDIR.EXE    - VDM Component.

GDI.EXE      - Modified version of Windows 3.10 GDI.EXE.
USER.EXE     - Modified version of Windows 3.10 USER.EXE.