Lecture 1&2: Introduction and Computer System Structure

Question 1

Define operating system

Answer 1

a program that acts as intermediary between user and computer hardware

Question 2

4 components of computer system

Answer 2

1. hardware - cpu, memory, I/O devices
2. operating system
3. application programs - web browser, compiler
4. users - people, machine

Question 3

handheld computer

Answer 3

• has poor resources
• optimized usability
• optimized battery life

Question 4

2 main uses of operating system

Answer 4

1. resource manager
   - manage all resources and decide between conflicting request
2. program controller
   - control program execution to prevent errors and improper uses of computer

Question 5

function of bootstrap program

Answer 5

• initialize all aspects of system
• load OS kernel
• start execution

Question 5

how computer system operation works

Answer 5

One or more CPU and device controller is connected through common bus providing access to shared memory
- each device controller has a local buffer
- CPU move data from/to main memory to/from local buffer
- I/O is from device to local buffer of controller
- device controller informs CPU finishing operation by causing interrupt

Question 6

what is trap

Answer 6

software-generated interrupt caused by user request or an error

Question 7

how to prevent lost interrupt

Answer 7

incoming interrupt is disabled while another interrupt is being processed

Question 7

2 types of interrupt

Answer 7

• pooling
• vectored-interrupt system

Question 8

what is system call

Answer 8

• request to OS to allow user wait for I/O completion

Question 9

how direct memory access structure works

Answer 9

• transmit information at close to memory speed
• device controller transfer block of data directly from buffer storage to main memory
• without CPU intervention

** only one interrupt is generated per block

Question 10

3 types of storage

Answer 10

• main storage (volatile)
• secondary storage (non-volatile)
• magnetic disks

Question 11

storage system heirachy

Answer 11

• speed
• cost
• volatility

Question 12

what is caching

Answer 12

transfer information into faster storage system

**main memory can be considered as cache of secondary storage

Question 13

advantages of multiprocessors

Answer 13

• increased reliability
• increased throughput
• economy of scale

Question 14

2 types of multiprocessing

Answer 14

• asymmetric
• symmetric

Question 15

symmetric clustering

Answer 15

multiple nodes running applications, monitoring each other

Question 16

asymmetric clustering

Answer 16

has one machine that in hot stand-by mode

Question 17

define clustered system

Answer 17

like multiprocessor system, but multiple system working together
- usually share data using SAN (storage area network)

Question 18

How multiprogramming works

Answer 18

• organized job so that CPU always has one to execute
• subset of total jobs are stored in memory
• one job is selected and run via job scheduling

Question 19

define multitasking (time-sharing)

Answer 19

logical extension which CPU switches job frequently allowing users to interact with each job while it is running, creating interactive computing

Question 20

time-sharing

Answer 20

• response time should be less than 1 second
• CPU scheduling allow several jobs run at a same time
• process: at least one program is executing in memory
• swapping when the process do not fit in memory
• virtual memory allow execution of process not only in memory

Question 21

what is dual mode

Answer 21

user mode and kernel mode

Question 22

function of system call

Answer 22

change mode to kernel

Question 23

define process

Answer 23

• program in execution

** program = passive entity, process = active entity

Question 24

process require resources

Answer 24

• CPU
• memory
• I/O
• files
• initialized data

Question 25

differentiate single-thread and multi-threaded

Answer 25

single-threaded:
- has one program counter specifying location of the next instruction
- execute instruction sequentially, one at a time

multi-threaded:
- has one program counter per thread

Question 26

process management activities

Answer 26

• creating and deleting
• suspending and resuming
• synchronization
• communication
• deadlock handling

Question 27

memory management activities

Answer 27

• decide which process to move in and our of the memory
• keep track of the memory currently used
• allocate and deallocate memory space

Question 28

file management activities

Answer 28

• creating and deleting files and directories
• manipulate
• mapping files to secondary storage
• backup files

Question 29

mass-storage management activities

Answer 29

• free space management
• storage allocation
• disk scheduling

Question 30

responsibility of I/O subsystem

Answer 30

• memory management of I/O
• general device-driver interface
• driver for specific hardware devices

Question 31

differentiate protection and security

Answer 31

protection: control access of process and user to resources
security: defense against internal and external attack

Question 32

3 types of network

Answer 32

• Wide Area Network (WAN)
• Local Area Network （LAN）
• Metropolitan Area Network (MAN)

Question 33

3 special purpose systems

Answer 33

• handheld
• multimedia
• real-time

Question 34

3 types of computing environment

Answer 34

1. server-client computing
2. peer-to-peer computing
3. web-based computing

Question 35

transition from user to kernel mode

Answer 35

timer is used to prevent infinite loop/process hogging resources
- set interrupt after specific period
- OS decrement counter
- generate interrupt when counter=0
- set before scheduling to regain control or terminate program that exceed allotted time

Question 36

special purpose system

Answer 36

• real-time embedded system
• handheld system
• multimedia system