CSCE4600 Exam 1

Question 1

The OS is responsible for

Answer 1

• Unify view of memory
• Transfer Data between CPU and other devices
• Keep track of file locations
• Provide HW / Platform Independence
• Mediate Resource Usage

Question 2

What are the 3 views of OS

Answer 2

Abstraction
Virtualization
Resource Management

Question 3

I/O primitives are…

Answer 3

system calls, executed by the kernal

Question 4

Name the 6 UNIX primitives

Answer 4

• create()
• open()
• close()
• read()
• write()
• ioctl()

Question 5

If pathname does not start with / it is assumed…

Answer 5

to start in the current directory

Question 6

if pathname starts with ./

Answer 6

current directory

Question 7

if pathname starts with ../

Answer 7

refers to the parent directory

Question 8

In Kernel mode, the executing code has..

Answer 8

complete and unrestricted access to the underlying hardware

Question 9

Generally reserved for the lowest-level, most trusted functions

Answer 9

Kernel mode

Question 10

In User mode, the executing code has…

Answer 10

no ability to directly access hardware or reference memory

Question 11

Advantage for user mode,

Answer 11

crashes in user mode are always recoverable

Question 12

Disadvantage for Kernel mode,

Answer 12

crashes are catastrophic

Question 13

Why is unbuffered I/O suffer a performance loss?

Answer 13

you read and/or write one byte at a time

Question 14

Buffered I/O is a net win when…

Answer 14

performing a large humber of small writes

Question 15

A program whose execution has started and not yet terminated

Answer 15

A process

Question 16

If all executions allowed under precedence relation result in the same values, then system is

Answer 16

Determinant

Question 17

for (Pi,Pj), Pi must…

Answer 17

complete before the start of Pj

Question 18

Mutually non-interfering systems ARE/AREN’T determinant

Answer 18

ARE

Question 19

Name the 7 parts of a process

Answer 19

1) Process State
2) Program counter
3) CPU registers
4) CPU scheduling
5) Memory management
6) Accounting information
7) I/O status

Question 20

Set of all processes in the system

Answer 20

Job queue

Question 21

set of all processes residing in main memory, ready and waiting

Answer 21

Ready queue

Question 22

set of processes waiting for an I/O device

Answer 22

device queue

Question 23

selects which processes should be brought into the ready queue

Answer 23

Long-term scheduler

Question 24

selects which process should be executed next and allocates CPU

Answer 24

Short-term scheduler

Question 25

spends more time doing I/O than computations, many short CPU bursts

Answer 25

I/O bound process

Question 26

spends more time doing computations, few very long CPU bursts

Answer 26

CPU-bound process

Question 27

Any code segment that accesses a shared data area is referred to as...

Answer 27

Critical Section

Question 28

solution to the Critical Section problem is to..

Answer 28

allow at most one process to be active, Mutual Exclusion

Question 29

A process that is currently not executing in its critical section must not prevent other processes to enter the critical section

Answer 29

Progress

Question 30

A process must not *repeatedly* enter its critical section, thereby preventing other processes to enter the critical section

Answer 30

Starvation

Question 31

two processes that are about to enter their critical section must not block each other indefinitely

Answer 31

Deadlock

Question 32

two processes about to enter their critical section must not repeatedly yield to each other indefinitely

Answer 32

Livelock

Question 33

Name a requirement for Critical Section problem

Answer 33

A thread which dies in its critical non-critical section will not affect the others' ability to continue.

Question 34

Changes a process from ready state to running state

Answer 34

Short-Term scheduler

Question 35

Another name for Short-term scheduler

Answer 35

CPU scheduler

Question 36

Removes the process from the memory

Answer 36

Medium-term scheduler

Question 37

In charge of handling the swapped out processes

Answer 37

Medium-term scheduler

Question 38

Name the three types of queues

Answer 38

Job queue Ready queue Device queues

Question 39

An analogy for synchronous communication

Answer 39

A phone call

Question 40

An analogy for asynchronous communication

Answer 40

A letter

Question 41

No blocking, so resources could be freed

Answer 41

Asynchronous Communication

Question 42

Requestor blocks, held resources are “tied up”. 

Answer 42

Synchronous communication

Question 43

Response times are unpredictable

Answer 43

Asynchronous communication

Question 44

Outcome is known immediately 

Answer 44

Synchronous communication

Question 45

If the system is | determinate for all interpretations...

Answer 45

then all processes are mutually non-interferring

Question 46

Every read and write will cause a context switch

Answer 46

Unbuffered I/O

Question 47

Collects as many bytes as you can before writing to file

Answer 47

Explicit buffered I/O

Question 48

Explicit buffered I/O uses...

Answer 48

UNIX I/O primitives

Question 49

Implicit buffered I/O uses...

Answer 49

Stream facility library

Question 50

allocates memory in the process table and creates a copy of the current process.

Answer 50

fork()

Question 51

used to terminate a process

Answer 51

exit()

Question 52

temporarily suspends parent process until one of the child processes has terminated

Answer 52

wait()

Question 53

used to execute the corresponding process

Answer 53

exec()

Question 54

A newly created child process returns

Answer 54

0

Question 55

the status in the wait() function is...

Answer 55

a pointer to an integer to which the child's status information is assigned

Question 56

how could read() fail

Answer 56

could fail if you try and access something you don’t have permissions to access

Question 57

how could write() fail

Answer 57

could fail if you don’t have adequate memory allocated to write to

Question 58

how could fork() fail

Answer 58

could fail if system has reached limit of total processes

Question 59

how could close() fail

Answer 59

can fail if file descriptor is invalid

Question 60

how could waitpid() fail

Answer 60

could fail if the called child process does not exist