Operating Systems Question Bank with Answers 11

What are the processor execution modes in operating systems and list the difference between them

Question:

List the processor (CPU) execution modes that are necessary for an OS that protects memory and hardware. What is the difference between them?

Answer:

At least two processor (CPU) execution modes are necessary for an operating system that protects memory and hardware.

• User/program mode and

• Kernel/supervisor/protected/privileged/system mode

Kernel mode provides access to all processor instructions. User mode cannot perform privileged instructions. If a privileged instruction is executed in user mode it causes an exception.

***********************

Related Questions:

• List the advantages of user–level threads

• List the disadvantage of user-level threads

• List the advantages of kernel-level threads

• List the disadvantages of kernel-level threads

• What are the typical uses of threads?

• What are user level and kernel level threads?

• What is the purpose of a system call? What mechanism is typically used to implement system calls?

• Compare and contrast on preemptive and non-preemptive scheduling approaches, on issues of simplicity, fairness, performance and required hardware support.

• What are the main steps performed by a file system when a process opens a file?

• List the processor (CPU) execution modes that are necessary for an OS that protects memory and hardware.What is the difference between them?

 What are the modes called and what is the difference between them.