All processes start as user mode. The kernel isnt a process, it's a controller of processes.

Process Scheduling:

The process scheduler is a part of the operating system that decides which process runs at a certain point in time. It usually has the ability to pause a running process, move it to the back of the running queue and start a new process; such a scheduler is known as preemptive scheduler, otherwise it is a cooperative scheduler.

Context Switching

The process by which the CPU is able to transition into executing another process.


  1. CPU Stops current operationa and switches to Kernel mode.
  2. CPU Records the current state of the CPU and memory.
  3. Kernel performs pending tasks (I/O,etc.).
  4. Kernel chooses a process based on a scheduling algorithm.
  5. Kernel prepares the memory for the next process and starts the next process execution.


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