Different levels software can be run at?

Originally Posted by ntwizard

I really don't so..

Jeff Richter the author of many Windows 32 programming manuals taught me this in the Advanced Windows Hardware Architecture classes I took while I was working at Intel...

It is also in Helen Custer's Inside Windows NT..

Since Windows NT still has compatability with OS/2, all three rings would be used..

Windows NT has limited compatibility with OS/2 (16 bit app only, no any privileged code like IOPL modules/dlls). OS/2 subsystem run only in Ring-3 like
VDM (DOS)