When a process is started in Windows NT 4.0, it will either have Normal priority for the environment it is running in, or it will have the priority specified in the START command.

When a program lauches a threat, it can specify a priority which is relative the parent process. While Windows NT can adjust a processes priority, all the threads will maintain their relative priority. Windows NT will never reduce a threads priority below the base priority it was launched at.

The Windows NT priorities are:



RELATIVE                  PROCESS PRIORITY CLASS
THREAD                Normal, in      Normal, in
PRIORITY       IDLE   BACKGROUND      FOREGROUND    HIGH    REALTIME

Time Critical   15        15              15         15        31
Highest          6         9              11         15        26
Above Normal     5         8              10         14        25
Normal           4         7               9         13        24
Below Normal     3         6               8         12        23
Lowest           2         5               7         11        22
Idle             1         1               1          1        16
See tip 269.