Lecture 3: OS Structure

Question 1

6 functions of OS for user

Answer 1

• user interface
• program execution
• file-system manipulation
• I/O operations
• communications
• error detections

Question 2

3 functions of OS for system

Answer 2

• accounting
• protection and security
• resource allocation

Question 3

define security

Answer 3

require user authentication to defense external I/O devices from invalid access attempts

Question 4

define protection

Answer 4

to control access of system resources

Question 5

Command Line Interface (CLI)

Answer 5

allows direct command entry
- primarily fetch a command in users and execute it

Question 6

Graphic User Interface (GUI)

Answer 6

user-friendly desktop metaphor interface
- icons represent files, program and action

Question 7

3 general methods to pass parameters to OS

Answer 7

• in register
• block method (parameter store in block in memory, and the address of block passed as a parameter in register)
• stack method (parameter placed onto a stack and popped off)

Question 8

5 types of system call

Answer 8

• process control (end, execute, wait event)
• file management (open, close, create, delete)
• device management (read, write, request, release)
• information maintenance (get and set date, time)
• communication (send and receive message, create and delete connection)

Question 9

define system programs

Answer 9

provide a convenient environment for program development and execution

Question 10

6 division of system programs

Answer 10

• file manipulation
• file modification
• status information
• communications
• programming language and support
• program loading and execution
• application program

Question 11

file manipulation

Answer 11

manipulate files and directories
- create, delete, copy, rename

Question 12

file modification

Answer 12

• text editors to create and modify files
• special command to search content of files

Question 13

status information

Answer 13

• ask system for information
• provide detailed performance, logging and debugging
• format and print the output to the terminal

Question 14

communications

Answer 14

to create virtual connections among processes, user, and computer system
- send message to other’s screen
- browse web

Question 15

program loading and execution

Answer 15

• absolute loader, reallocate loader, linkage editor, debugging system

Question 16

programming language and support

Answer 16

• provide compiler, assembler, debugger and interpreters

Question 17

2 goals in designing and implementing OS

Answer 17

User goals
- easy to learn, convenient to use, reliable, fast and safe

system goals
- easy to design, implement and maintain
- flexible, reliable, error-free, efficient

Question 18

how microkernel system structure works

Answer 18

move as much from kernel space to user space
- communication take place between user modules using message passing

Question 19

benefits of microkernel system structure

Answer 19

• easier to extend the microkernel
• easier to port the OS to new architecture
• more reliable as less code is store in kernel
• more secure

Question 20

disadvantages of microkernel system structure

Answer 20

performance may overhead the user space and kernel space communication

Question 21

virtual machines

Answer 21

• using layered approach
• treat both hardware and software as all hardware
• provide interfaces indentical to underlying hardware
• create illlusion that all process has its own processers and virtual memory

Question 22

why virtualisation is hard to implement

Answer 22

• exact duplication of underlying machine is needed
• typically run in user modes
• timing is slower than real machine
• hardware support needed

Question 23

benefits of virtual machine

Answer 23

• file sharing can be controlled and permitted
• multiple execution environment can share the same hardware
• protected from each other
• allow communication with each other via networking
• consolidation of low-resource used program into fewer busier system