Question

In operating system;

‘What happens in a context switch?

Answer 1

ANSWER -

An Operating system is a program that acts as an interface between the user of the computer and the computer hardware, the main purpose of operating system is to provide an environment for the user so that they can execute required program in a convenient and efficient way.

Context switching - The transferring of control of CPU from one process to another device saving the context from currently running process and loading the context of another already process. This mechanics of saving and reloading the context is known as context switching or context switch.

The portion of Process Control Block (PCB) which includes the process state, memory management information and CPU scheduling information together constitute the context of process.

Context switch can occur in the following situation -

• Currently executing process terminates and exit from the system.
• Currently executing process expires due to time slice (milliseconds).
• Some of higher priority processes enters the system.
• The process has to wait for some resources.

The context switching can be performed in two steps ,

1. Save the context - In this step, the currently executing process context is saved by the kernel in the process control block so that it can reload its context later.
2. Reload the context - In this step, the saved context is loaded by the kernel of different process so that it can be executed next.

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