Operating System Set 18 MCQs

Q1 | Virtual memory allows

execution of a process that may not be completely in memory

a program to be smaller than the physical memory

a program to be larger than the secondary storage

execution of a process without being in physical memory

Q2 | A process is thrashing if

it is spending more time paging than executing

it is spending less time paging than executing

page fault occurs

swapping can not take place

Q3 | The ability to execute a program that is only partially in memory has benefits like

the amount of physical memory cannot put a constraint on the program

programs for an extremely large virtual space can be created

throughput increases

all of the mentioned

Q4 | Virtual memory is normally implemented by

demand paging

buses

virtualization

all of the mentioned

Q5 | Segment replacement algorithms are more complex than page replacement algorithms because

segments are better than pages

pages are better than segments

segments have variable sizes

segments have fixed sizes

Q6 | A swapper manipulates whereas the pager is concerned with individual of a process.

the entire process, parts

all the pages of a process, segments

the entire process, pages

none of the mentioned

Q7 | Using a pager

increases the swap time

decreases the swap time

decreases the swap time & amount of physical memory needed

increases the amount of physical memory needed

Q8 | The valid – invalid bit, in this case, when valid indicates?

the page is not legal

the page is illegal

the page is in memory

the page is not in memory

Q9 | A page fault occurs when?

a page gives inconsistent data

a page cannot be accessed due to its absence from memory

a page is invisible

all of the mentioned

Q10 | When a page fault occurs, the state of the interrupted process is

disrupted

invalid

saved

none of the mentioned

Q11 | When a process begins execution with no pages in memory?

process execution becomes impossible

a page fault occurs for every page brought into memory

process causes system crash

none of the mentioned

Q12 | If the memory access time is denoted by ‘ma’ and ‘p’ is the probability of a page fault (0 <= p <= 1). Then the effective access time for a demand paged memory is

p x ma + (1-p) x page fault time

ma + page fault time

(1-p) x ma + p x page fault time

none of the mentioned

Q13 | When the page fault rate is low

the turnaround time increases

the effective access time increases

the effective access time decreases

turnaround time & effective access time increases

Q14 | Locality of reference implies that the page reference being made by a process

will always be to the page used in the previous page reference

is likely to be one of the pages used in the last few page references

will always be one of the pages existing in memory

will always lead to page faults

Q15 | Which of the following page replacement algorithms suffers from Belady’s Anomaly?

optimal replacement

lru

fifo

both optimal replacement and fifo

Q16 | In question 2, if the number of page frames is increased to 4, then the number of page transfers

decreases

increases

remains the same

none of the mentioned

Q17 | A memory page containing a heavily used variable that was initialized very early and is in constant use is removed, then the page replacement algorithm used is

lru

lfu

fifo

none of the mentioned

Q18 | Users that their processes are running on a paged system.

are aware

are unaware

may unaware

none of the mentioned

Q19 | If no frames are free, page transfer(s) is/are required.

one

two

three

four

Q20 | A FIFO replacement algorithm associates with each page the

time it was brought into memory

size of the page in memory

page after and before it

all of the mentioned

Q21 | What is the Optimal page – replacement algorithm?

replace the page that has not been used for a long time

replace the page that has been used for a long time

replace the page that will not be used for a long time

none of the mentioned

Q22 | LRU page – replacement algorithm associates with each page the

time it was brought into memory

the time of that page’s last use

page after and before it

all of the mentioned

Q23 | What are the two methods of the LRU page replacement policy that can be implemented in hardware?

counters

ram & registers

stack & counters

registers

Q24 | When using counters to implement LRU, we replace the page with the

smallest time value

largest time value

greatest size

none of the mentioned

Q25 | There is a set of page replacement algorithms that can never exhibit Belady’s Anomaly, called

queue algorithms

stack algorithms

string algorithms

none of the mentioned