PART 1 - INTRODUCTION

Question 1

What Is an Operating System?

Answer 1

Computer consists of some or all of:

• Processors
• Main memory
• Disk
• Various input/output device/interface

Managing all these components require a layer of software - the Operating System

Question 2

What are the two main functions of an OS?

Answer 2

1) It is an extended Virtual Machine

2) It is a resource manager

Question 3

How does the OS operates as an extended machine?

Answer 3

It provides usable abstractions for complex/difficult to use hardware

Question 4

How does the OS operates as a resource manager?

Answer 4

• The OS allow multiple programs to run at the same time
• It manages and protects memory, I/O devices and other resources
• It shares resources in two ways:
  1) In time
  2) In space

Question 5

What is a process?

Answer 5

A Process is the key operating system abstraction.

A process is a program in execution.

Each process has an address space.

• Memory locations the process can read and write.
• Executable program text, program data and its stack (one frame per active procedure).

Question 6

Monolythic vs Microkernel

Answer 6

Traditionally all OS layers are in kernel
– But kernel bugs bring whole system down
– In monolithic systems a bug in an audio driver can crash the system
➔ Put as little as possible in kernel mode

• Microkernels
– Split OS into small, well-defined modules
– Run only one essential module in kernel mode (the microkernel for process management, IPC etc.)
– Device drivers, filesystem etc. are separate user mode processes
• Bug in audio driver will garble sound not the system!