CODEWITHSUNDEEP
operating-systemcpu-architecture
Mathews George
Mathews George

Reputation: 47

How is it possible for OS processes to manage User processes while they themselves are processes?

Recently, I have been reading about Operating Systems, and this bugs me a lot. How is it really possible for one process to manage other process.

Basically a CPU simply executes instructions, after executing one instruction, then it executes the instruction at address pointed by IP and increments the IP.

Let me elaborate my doubt with an example. Lets say I have an User process (or simply a process) which is being executed by CPU. Lets say, it has 'n' instruction and currently executing 'i'th instruction. IP points to (i+1)th instruction. So, at this point how can all other OS processes like Scheduler, dispatcher etc... comes into play, Since CPU is already executing another process.

One solution (Just a guess), I could think of is , the use of Interrupts and Interrupt Service Routines.

But its only a guess.

PS: I searched and couldn't find any satisfying answer.

Upvotes: 1

Views: 146

Answers (1)

Tony Tannous
Tony Tannous

Reputation: 14863

With the help of the hardware, ticks causes the CPU to execute operating system code. This code checks the system state and the time that has elapsed since the beginning of this process execution. At this point, the operating system can decide to schedule a different process. All it has to do is save the current state of the running process with the process that is about to start running. (basically changing the content of the registers and saving the registers state before changing to the new process).
Eventually, the CPU is taken away even if the process doesn't want to yield it.

To address your concern, there are no operating system processes in the way you think... it isn't like there are OS processes in the queue waiting among other processes....

Upvotes: 2

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