Just out of curiosity what are the processes between 0 and 4, and also between 4 and 200 something.
2 Answers
There is no Process ID 1,2,or3 because of how the NT kernel handle table works.
Handles are always multiples of four. The Kernel handle process object is used for both process handles and process/thread IDs. It happens that handle values all start at 0x4 (bit 2), and the InitialSystemProcess is the first process to be created, so it gets a PID of 4. Idle process isn't actually a process and you can't open it. It probably doesn't have a real PID but most tools consider it to be 0.
More on the NT handle table here although this is only accurate for NT3-5(xp) , as Windows 7 now requires that you only reference kernel handles if attached to PsInitialSystemProcess.
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7Hmm thats interesting, i never realized that all the pids were divisible by 4– agzMar 26, 2013 at 7:34
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@agz: The numbers between 4 and 200-ish (and many more) are in semi-permanent use by threads in the so-called System process. Process and thread IDs (generically called "client IDs") come from the same "number space". You can see thread IDs in Process Explorer: Double-click on a process, then look at the Threads tab in the resulting "Properties" window. Apr 25, 2015 at 21:18
you can see all of that processes between 4 and 200 and many more in the Process Explorer System process - properties - threads pane.