in Operating System1.Why are two modes (user and kernel) needed?2.What are the steps performed by an OS to create a new process?3.What is the difference between an interrupt and a trap?4.Give three examples of an interrupt.5.What is the difference between a mode switch and a process switch?

Question
Asked Feb 7, 2019

in Operating System
1.Why are two modes (user and kernel) needed?
2.What are the steps performed by an OS to create a new process?
3.What is the difference between an interrupt and a trap?
4.Give three examples of an interrupt.
5.What is the difference between a mode switch and a process switch?

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Expert Answer

Step 1

Reasons why two modes are needed in OS:

The two modes of OS are user mode and kernel mode. The user mode helps the operating system in running user applications. The kernel model is required when the system boots and operating system is loaded. Some of the privileged instructions work in kernel mode only. These two modes are required to avoid some issues like a running program can wipe out the operating system accidentally by overwriting it with user data and some disaster results can be occurred due to multiple processes writing in the same system at same time.

Step 2

Steps performed by an OS to create a new process are:

  • A process is created by other process through system calls like spawn or fork. The new created process is called as child process and the process created the new process is called as parent process.
  • Every process is given a unique identifier called as process identifier or PID.
  • In a UNIX system, the process scheduler called as sched is given PID 0. At the time of system startup, it first launches init which is given PID 1. Then init becomes parent by launching all system daemons and user logins.
  • Based on system implementation, child process gest some of resources from parent process.
Step 3

Difference between Interrupt and Trap:

The key difference between trap and interrupt is that trap is a kind of software interrupt triggered by user program like invalid memory access or division b...

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