Win32 Base Priority Classes
Constant Value Description
WIN32_ABOVE_NORMAL_PRIORITY_CLASS 0x00008000 Process that has priority above WIN32_NORMAL_PRIORITY_CLASS but below WIN32_HIGH_PRIORITY_CLASS.
WIN32_BELOW_NORMAL_PRIORITY_CLASS 0x00004000 Process that has priority above WIN32_IDLE_PRIORITY_CLASS but below WIN32_NORMAL_PRIORITY_CLASS.
WIN32_HIGH_PRIORITY_CLASS 0x00000080 Process that performs time-critical tasks that must be executed immediately. The threads of the process preempt the threads of normal or idle priority class processes. An example is the Task List, which must respond quickly when called by the user, regardless of the load on the operating system. Use extreme care when using the high-priority class, because a high-priority class application can use nearly all available CPU time.
WIN32_IDLE_PRIORITY_CLASS 0x00000040 Process whose threads run only when the system is idle. The threads of the process are preempted by the threads of any process running in a higher priority class. An example is a screen saver. The idle-priority class is inherited by child processes.
WIN32_NORMAL_PRIORITY_CLASS 0x00000020 Process with no special scheduling needs.
WIN32_REALTIME_PRIORITY_CLASS 0x00000100 Process that has the highest possible priority. The threads of the process preempt the threads of all other processes, including operating system processes performing important tasks. For example, a real-time process that executes for more than a very brief interval can cause disk caches not to flush or cause the mouse to be unresponsive.