The % Total User Time is the average percentage of time spent in User mode by all processors. On a multi-processor system, if all processors are always in User mode this is 100%, if all processors are 50% in User mode this is 50% and if 1/4th of the processors are in User mode this is 25%. Applications execute in User Mode, as do subsystems like the window manager and the graphics engine. Code executing in User Mode cannot damage the integrity of the Windows NT Executive, Kernel, and device drivers. Unlike some early operating systems, Windows NT uses process boundaries for subsystem protection in addition to the traditional protection of User and Privileged modes. These subsystem processes provide additional protection. Therefore, some work done by Windows NT on behalf of an application may appear in other subsystem processes in addition to the Privileged Time in the application process.