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