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Windows Process ID

Each process is identified by a numberical (integer value), named ID, process id, process identifier or simply PID.

These process IDs are always multiple of 4 because they (somehow) relate to handles in the Kernel which themselves are always multiple of 4.

This statement can be «verified» with the following PowerShell pipeline:

get-process | where-object { [Math]::Round($_.id /4 ) -ne ($_.id/4) }

Processes with PID 0 and 4

The process with the PID 0 is the System Idle Process. Technically, it is not a process, and it never exists.

The process with PID 4 is the first process that is created (and becuase PIDs are always multiple of 4). This process is the System Process.