Chapter 1

Question 1

What is OS basic

Answer 1

A large program

Question 2

What does OS manage

Answer 2

Computer hardware resources, decides between conflicting requests for efficient and fair resource use

Question 3

What kind of program is OS

Answer 3

Control

Question 4

What is relationship of OS between user of computer and computer hardware

Answer 4

Intermediary

Question 5

Why does OS control execution of programs?

Answer 5

To prevent errors and improper use of the computer

Question 6

What does CPU repeat?

Answer 6

Cycle of fetching and executing low level machine instructions

Question 7

OS goals for user

Answer 7

Execute user programs and make it easy and convenient

Question 8

OS goals system/Hardware

Answer 8

Manage resources and use computer hardware efficiently

Question 9

OS Abstraction

Answer 9

The act of removing unimportant details or attributes of objects in order to construct more general and less complex objects

Question 10

OS Virtualization

Answer 10

The act of creating the illusion of having one or more objects with more desirable characteristics than the real object.

Question 11

How does OS use abstraction?

Answer 11

Multiple operations at one level are combined into a single operation at a higher level, making it easier to use

Question 12

How does OS use virtualization?

Answer 12

Create virtual CPUs, memory, I/O devices

Question 13

Batch Processing

Answer 13

Method of running software programs(jobs) in batches automatically with no user interaction required

Question 14

4 Major OS components

Answer 14

1. Processes and Threads
2. CPU Scheduling
3. I/O Management
4. Memory Management

Question 15

Multiprogramming

Answer 15

Technique that keeps several programs active in memory and switches execution among the different programs to maximize the use of the CPU and other resources

Question 16

Multiprogramming example

Answer 16

When a program enters IO phase then another program can utilize the CPU

Question 17

Time-sharing (multi-tasking)

Answer 17

Extension of multiprogramming where the CPU switches jobs so frequently that users can interact with each job while it is running

Question 18

What does time-sharing create

Answer 18

interactive computing

Question 19

Time-sharing employs concept of

Answer 19

Virtualization by creating illusion of having a separate virtual CPU for each computation

Question 20

Can abstraction be used without virtualization

Answer 20

Yes

Question 21

Can virtualization be used without abstraction

Answer 21

No

Question 22

Can abstraction and virtualization be used together

Answer 22

Yes

Question 23

Process

Answer 23

Program in execution

Question 24

Multitasking gives the _ of _ on one cpu

Answer 24

Illusion of parallel processing

Question 25

The OS creates and deletes

Answer 25

Processes and threads

Question 26

The OS suspends and resumes

Answer 26

Processes and threads

Question 27

The OS schedules

Answer 27

Processes and threads

Question 28

The OS provides mechanisms for 3

Answer 28

Process Synchronization Interprocess communication Deadlock Handling

Question 29

I/O management synchronous

Answer 29

Control returns to the user program only upon I/O completion Wait loop until next interrupt

Question 30

I/O management asynchronous

Answer 30

Control returns to user program without waiting for I/O completion Does this through signal or callback

Question 31

OS 5 design approaches

Answer 31

Simple, Layered, Microkernels, Modular, Hybrid

Question 32

Simple Structure

Answer 32

No defined layers or modules, starts small and grows in complexity over time

Question 33

Monolithic operating system

Answer 33

Design where entire operating system is implemented as a single large program running in a single address space (kernel mode)

Question 34

Layered approach

Answer 34

The OS is divided into a series of hierarchical layers, each building on the lower layers, with each layer interacting with only the one directly beneath it

Question 35

Single Layered

Answer 35

Enormous amount of functionality crammed into the kernel, no encapsulation

Question 36

Full layered approach

Answer 36

The OS is divided into a number of layers, each built on top of lower layers

Question 37

Layered approach advantage

Answer 37

Layers can be debugged and replaced independently without bothering the other layers above or below

Question 38

Layered approach cons

Answer 38

Appropriately defining the various layers More overhead

Question 39

Microkernels

Answer 39

Reduces the size of the kernel to include only essential OS functions

Question 40

Microkernels idea

Answer 40

Minimize the kernel by moving as much functionality as possible from the kernel into user space

Question 41

Microkernel pros

Answer 41

Easier to extend, more portable, and more reliable

Question 42

Microkernel cons

Answer 42

Performance overhead due to frequent communication between user space and kernel, Not always realistic, some functions must remain in kernel space

Question 43

Modular

Answer 43

A kernel design in which the OS is built from separate modules all within kernel

Question 44

Kernel

Answer 44

The minimal set of functions necessary to manage the system resources safely and efficiently.

Question 45

Privileged Instruction

Answer 45

Performs critical operations that access I/O devices and the CPU's status and control registers

Question 46

Who is allowed to use privileged instructions

Answer 46

Only OS kernel

Question 47

Kernel Mode

Answer 47

CPU state where both privileged and nonprivileged instructions may be used

Question 48

User Mode

Answer 48

CPU state where only nonprivileged instructions may be used

Question 49

Any attempt to use privileged instruction in user mode automatically

Answer 49

transfers control to kernel mode

Question 50

OS Shell

Answer 50

Command interpreter that accepts and interprets textual commands issued by the user via a keyboard

Question 51

System Call

Answer 51

A request from an application for an OS service

Question 52

Supervisor call (kernel call)

Answer 52

privileged instruction that automatically transfers execution control to a well defined location in the OS kernel

Question 53

Interrupt

Answer 53

An event that diverts the current execution of a program to a predefined location in the kernel in order to respond to an event

Question 54

Two popular uses of interrupt

Answer 54

Signal to OS completion of IO event Implement time sharing by periodically switching the PCU among multiple concurrent computations

Question 55

Trap

Answer 55

Interrupt triggered by currently executing instruction