Windows NT 4.0 has a flat, linear 32-bit memory. This means that each program can see 32 bits of address space or 4 gigabytes of virtual memory. The upper half of virtual memory is reserved for system code and data that is visible to the process only when it is running in privileged mode. The lower half is available to the program when it is running in user mode and to user-mode system services called by the program.
Note
Windows NT versions prior to 3.51 included some 16-bit data structures that limited processes to 256 MB (64K pages) of virtual memory. These have been converted to 32-bit data structures, so 2 gigabytes of virtual memory is available to all processes.JBJB
Monitoring Windows 4.0 memory requires that you understand both the concepts used to discuss it and the Performance Monitor counters used to test it.