Session 2

Question 1

OS is a _______ _______ and a _______ _______

Answer 1

OS is a control program and a resource allocator

Question 2

OS Controls execution of _______ to prevent errors and _______ use of the _______

Answer 2

Controls execution of programs to prevent errors and improper use of the computer.

Question 3

OS Manages all _______

Decides between conflicting _______ for _______ and fair _______ use

Answer 3

OS Manages all resources

Decides between conflicting requests for efficient and fair resource use

Question 4

Defining OS

Answer 4

A special piece of software that Abstracts and Arbitrates the use of a computer system.

Question 5

OS Elements

__________

Process, File, Thread, Socket, Memory Page.

Answer 5

OS Elements

Abstraction

Process, File, Thread, Socket, Memory Page.

Question 6

OS Elements

__________ –How to do it??

Create, schedule, open, write, allocate.

Answer 6

OS Elements

Mechanism –How to do it??

Create, schedule, open, write, allocate.

Question 7

OS Elements

__________ –What will be done??

Least Recently User, Earliest Deadline First

Answer 7

OS Elements

Policies –What will be done??

Least Recently User, Earliest Deadline First

Question 8

Operating System Structure

__________
Only one or two levels of code.

Answer 8

Operating System Structure

Simple
Only one or two levels of code.

Question 9

Operating System Structure

__________
Independent Layers.

Answer 9

Operating System Structure

Layered
Independent Layers.

Question 10

Operating System Structure

__________
OS built from many user level processes.

Answer 10

Operating System Structure

Microkernel
OS built from many user level processes.

Question 11

Operating System Structure

__________
Core kernel with dynamically loadable modules.

Answer 11

Operating System Structure

Modular
Core kernel with dynamically loadable modules.

Question 12

Operating-System Operations

_____ _____- Interrupt ,trap or System call

Question???
When you are at home dozing your chair, how do you know when someone wants to talk to you on the phone?

A)Periodically pick up the phone to see if someone called. - _____

B) Or do you wait till the phone rings to answer it? - _____

Answer 12

Operating-System Operations

Event driven - Interrupt ,trap or System call

Question???
When you are at home dozing your chair, how do you know when someone wants to talk to you on the phone?

A)Periodically pick up the phone to see if someone called. - polling

B) Or do you wait till the phone rings to answer it? - interrupt

Question 13

Interrupt

_____ sends a special _____ to CPU when _____arrives.

Answer 13

Interrupt

Device sends a special signal to CPU when data arrives.

Question 14

Interrupt

Responds to _____ _____signal by _____ current _____.

Answer 14

Interrupt

Responds to hardware interrupt signal by interrupting current process.

Question 15

System Call

A system call is invoked in a variety of ways, depending on the _______ provided by the underlying _______. It is the method used by a _______to request _______by the operating system.

Answer 15

System Call

A system call is invoked in a variety of ways, depending on the functionality provided by the underlying processor. It is the method used by a process to request action by the operating system.

Question 16

System Call

Instruction which causes the _______ to change _______ .

Answer 16

System Call

Instruction which causes the processor to change mode .

Question 17

Timer Interrupt

How to prevent Infinite loop ???

Answer 17

Sets interrupts on specific periods (fixed timer)
Uses Counters (variable timer)

Question 18

Timer Interrupt

How to prevent Process Hogging???

Answer 18

Before turning over control to the user, the operating system ensures that the timer is set to interrupt.

Question 19

Process Management

A process is a _______ in _______ . It is a unit of _______ within the system.

Answer 19

Process Management

A process is a program in execution. It is a unit of work within the system.

Question 20

Process Management

Program is a _______ entity, process is an _______ entity.

Answer 20

Process Management

Program is a passive entity, process is an active entity.

Question 21

Process Management

A process needs certain _______—

• including CPU time, memory, files, and I/O devices—to accomplish its _______.

Answer 21

Process Management

A process needs certain resources—
including CPU time, memory, files, and I/O devices—to accomplish its task.

Question 22

Process Management

Multi-threaded Process – Each _______ has its own _______ Counter.

Answer 22

Process Management

Multi-threaded Process – Each thread has its own Program Counter.

Question 23

Process Management

Single-threaded process – one _______ counter

Answer 23

Process Management

Single-threaded process – one Program counter

Question 24

Process Management Activities

Scheduling _______ and _______ on the CPUs .

Creating and deleting both user and system _______.

_______ and resuming processes.

Providing mechanisms for process _______.

Providing _______ for process communication.

Answer 24

Process Management Activities

Scheduling processes and threads on the CPUs .

Creating and deleting both user and system processes.

Suspending and resuming processes.

Providing mechanisms for process synchronization.

Providing mechanisms for process communication.

Question 25

Memory Management

All _______ in _______ before and after processing

All _______ in _______ in order to execute

Memory management determines what is in _______ when Optimizing CPU utilization and computer response to _______

Memory management activities: Keeping track of which parts of _______ are _______ being used and by _______

Deciding which _______ (or a part of) and _______ to move into and out of _______

_______ and _______ memory space as needed

Answer 25

Memory Management

All data in memory before and after processing

All instructions in memory in order to execute

Memory management determines what is in memory when

Optimizing CPU utilization and computer response to users

Memory management activities

Keeping track of which parts of memory are currently being used and by whom

Deciding which processes (or a part of) and data to move into and out of memory

Allocating and deallocating memory space as needed

Question 26

Storage Management

OS provides uniform, logical view of information storage

_______ physical properties to logical storage unit - file
Each medium is controlled by device (i.e., disk drive, tape drive)

Varying properties include access speed, capacity, data-transfer rate, access method (sequential or random)

Answer 26

Storage Management

OS provides uniform, logical view of information storage

Abstracts physical properties to logical storage unit - file
Each medium is controlled by device (i.e., disk drive, tape drive)

Varying properties include access speed, capacity, data-transfer rate, access method (sequential or random)

Question 27

Storage Management

File-System _______
Files usually organized into directories
Access _______ on most systems to determine who can access what

OS activities include
Creating and deleting files and directories
Primitives to manipulate files and dirs
Mapping files onto secondary storage
Backup files onto stable (non-volatile) storage media

Answer 27

Storage Management

File-System management
Files usually organized into directories
Access control on most systems to determine who can access what

OS activities include
Creating and deleting files and directories
Primitives to manipulate files and dirs
Mapping files onto secondary storage
Backup files onto stable (non-volatile) storage media

Question 28

Mass-Storage Management

Usually disks used to store data that does not fit in _______ _______ or _______ that must be kept for a “long” period of time.

Proper _______ is of central importance

Entire speed of computer operation hinges on disk _______ and its _______

OS activities
Free-space management
Storage allocation
Disk scheduling

Some storage need not be fast
Tertiary storage includes optical storage, magnetic tape
Varies between WORM (write-once, read-many-times) and RW (read-write)

Answer 28

Mass-Storage Management

Usually disks used to store data that does not fit in main memory or data that must be kept for a “long” period of time.

Proper management is of central importance

Entire speed of computer operation hinges on disk subsystem and its algorithms

OS activities
Free-space management
Storage allocation
Disk scheduling

Some storage need not be fast
Tertiary storage includes optical storage, magnetic tape
Varies between WORM (write-once, read-many-times) and RW (read-write)

Question 29

I/O Subsystem

One purpose of OS is to hide peculiarities of _______ devices from the _______

I/O subsystem responsible for
- _______ _______ of I/O including _______(storing data temporarily while it is being transferred), _______(storing parts of data in faster storage for performance), _______ (the overlapping of output of one job with input of other jobs)

• General device-driver interface
• Drivers for specific hardware devices

Answer 29

I/O Subsystem

One purpose of OS is to hide peculiarities of hardware devices from the user

I/O subsystem responsible for
Memory management of I/O including buffering (storing data temporarily while it is being transferred), caching (storing parts of data in faster storage for performance), spooling (the overlapping of output of one job with input of other jobs)
General device-driver interface
Drivers for specific hardware devices

Question 30

Protection – any _______ for controlling _______of _______ or users to _______ defined by the OS

Answer 30

Protection – any mechanism for controlling access of processes or users to resources defined by the OS

Question 31

Protection –

Answer 31

any mechanism for controlling access of processes or users to resources defined by the OS

Question 32

Security – _______ of the system against internal and external attacks
Huge range, including denial-of-service, viruses, identity theft, theft of service.

Answer 32

Security – defense of the system against internal and external attacks
Huge range, including denial-of-service, viruses, identity theft, theft of service.

Question 33

Security –

Answer 33

Security – defense of the system against internal and external attacks
Huge range, including denial-of-service, viruses, identity theft, theft of service.

Question 34

Systems generally first distinguish among users, to determine who can do what

User identities (_______ , security IDs) include name and associated number, one per user

User ID then associated with all files, processes of that user to determine access control

Group identifier (_______ ) allows set of users to be defined and controls managed, then also associated with each process, file

_______ _______ allows user to change to effective ID with more rights

Answer 34

Systems generally first distinguish among users, to determine who can do what

User identities (user IDs, security IDs) include name and associated number, one per user

User ID then associated with all files, processes of that user to determine access control

Group identifier (group ID) allows set of users to be defined and controls managed, then also associated with each process, file

Privilege escalation allows user to change to effective ID with more rights