Infosys Test Paper 5

1. Father's age is three years more than three times the son's age. After three years, father's age will be ten years more than twice the son's age. What is the father's present age.
Ans: 33 years
2. Find the values of each of the alphabets.
N O O N S O O N+ M O O N ---------- J U N E
Ans:
3. There are 20 poles with a constant distance between each pole A car takes 24 second to reach the 12th pole. How much will it take to reach the last pole.
Ans: 41.45 seconds (2 marks) Let the distance between two poles = x Hence 11x:24::19x:?

4. A car is travelling at a uniform speed. The driver sees a milestone showing a 2-digit number. After travelling for an hour the driver sees another milestone with the same digits in reverse order. After another hour the driver sees another milestone containing the same two digits. What is the average speed of the driver.
Ans: 45 kmph (4 marks)

5. The minute and the hour hand of a watch meet every 65 minutes. How much does the watch lose or gain time and by how much?
Ans: Gains; 5/11

6. Ram, Shyam and Gumnaam are friends. Ram is a widower and lives alone and his sister takes care of him. Shyam is a bachelor and his neice cooks his food and looks after his house. Gumnaam is married to Gita and lives in large house in the same town. Gita gives the idea that all of them could stay together in the house and share monthly expenses equally. During their first month of living together, each person contributed Rs.25. At the end of the month, it was found that Rs 92 was the expense so the remaining amount was distributed equally among everyone. The distribution was such that everyone recieved a whole number of Rupees. How much did each person recieve?
Ans. Rs (Hint: Ram's sister, Shyam's neice and Gumnaam's wife are the same person)

7. Four persons A, B, C and D are playing cards. Each person has one card, laid down on the table below him, which has two different colours on either side. The colours visible on the table are Red, Green, Red and Blue. They see the color on the reverse side and give the following comment.
A: Yellow or GreenB: Neither Blue nor GreenC: Blue or YellowD: Blue or Yellow
Given that out of the 4 people 2 always lie find out the colours on the cards each person.

Infosys Test Paper 4

INFOSYS
1) There are two balls touching each other circumferencically.
The radius of the big ball is 4 times the diameter of the small
ball.The outer small ball rotates in anticlockwise direction
circumferencically over the bigger one at the rate of 16 rev/sec.
The bigger wheel also rotates anticlockwise at Nrev/sec. what is
'N' for the horizontal line from the centre of small wheel always
is horizontal.
2) 1 2 3 4
+ 3 4 5 5
----------
4 6 8 9
- 2 3 4 5
----------
2 3 4 4
+ 1 2 5 4
------------
3 6 9 8
Q) Strike off any digit from each number in seven rows (need not
be at same place) and combine the same operations with 3 digit numbers
to get the same addition. After this strike off another digit from all
and add all the No.s to get the same 2 digit No. perform the same
process again with 1 digit No.s. Give the ' no.s in 7 rows at
each stage.
3) there is a safe with a 5 digit No. The 4th digit is 4 greater than
second digit, while 3rd digit is 3 less than 2nd digit. The 1st digit
is thrice the last digit. There are 3 pairs whose sum is 11. Find
the number. Ans) 65292.
4) there are 2 guards Bal and Pal walking on the side of a wall of a
wearhouse(12m X 11m) in opposite directions. They meet at a point and
Bal says to Pal " See you again in the other side". After a few moments
of walking Bal decides to go back for a smoke but he changes his
direction again to his previous one after 10 minutes of walking in
the other(opposite) direction remembering that Pal will be waiting
for to meet.If Bal and Pal walk 8 and 11 feet respectively, how
much distance they would have travelled before meeting again.
5) xxx)xxxxx(xxx
3xx
-------
xxx
x3x
------
xxx
3xx
------
Q) Find the 5 digit No.
Hint: 5 is used atleast once in the calculation.
6) Afly is there 1 feet below the ceiling right across a wall length
is 30m at equal distance from both the ends. There is a spider 1 feet
above floor right across the long wall eqidistant from both the ends.
If the width of the room is 12m and 12m, what distance is to be
travelled by the spider to catch the fly? if it takes the shortest
path.
7) Ramesh sit around a round table with some other men. He has one
rupee more than his right person and this person in turn has 1 rupee
more than the person to his right and so on, Ramesh decided to give
1 rupee to his right & he in turn 2 rupees to his right and 3 rupees
to his right & so on. This process went on till a person has
'no money' to give to his right. At this time he has 4 times the
money to his right person. How many men are there along with Ramesh
and what is the money with poorest fellow.
8)Question related to probabilities of removing the red ball from a
basket,given that two balls are removed from the basket and the other
ball is red. The basket contains blue,red,yellow balls.
9)Venkat has 1boy&2daughters.The product of these children age is 72.
The sum of their ages give the door numberof Venkat.Boy is elder of
three.Can you tell the ages of all the three.
ANALYTICAL
----------
1)L:says all of my other 4 friends have money
M:says that P said that exact one has money
N:says that L said that precisely two have money
O:says that M said that 3 of others have money.
P:Land N said that they have money.
all are liers.Who has money&who doesn't have?
2)A hotel has two,the east wing and the west wing.some east wing rooms
but not all have an ocean view(OV).All WW have a harbour view(HV).The
charge for all rooms is identical, except as follows
* Extra charge for all HV rooms on or above the 3rd floor
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infotest5
* Extra charge for all OV rooms except those without balcony
* Extra charge for some HV rooms on the first two floor&some EW rooms
without OV but having kitchen facilities. (GRE modrl Test 3-question
1J-22)
3)Post man has a data of name surname door no.pet name of 4 families.
But only one is correct for each family.There are a set of statements
&questions.
4)4 couples have a party.Depending on the set of statements,find who
insulted whom and who is the host of the party.
5)5 women given some of their heights(tall,medium,short)Hair( long,
plainted),stards(Black or Brown), sari,2 medium,2-short.Tall->no
sari.Plainted->medium.Answer the combinations.
1) A person has to go both Northwards&Southwards in search of a job.
He decides to go by the first train he encounters. There are trains for
every 15 min both southwards and northwards. First train towards south is at 6:00 A.M. and that towards North is at 6:10 .If the person arrives at any random time,what is the probability that he gets into a train towards North.
2) A person has his own coach&whenever he goes to railway station he
takes his coach.One day he was supposed to reach the railway station
at 5 O'clock. But he finished his work early and reached at 3O'clock.
Then he rung up his residence and asked to send the coach immediately. He came to know that the coach has left just now to the railway station. He thought that the coach has left just now to the railway station. He thought that he should not waste his time and started moving towards his residence at the speed of 3mi/hr.On the way,he gets the coach and reaches home at 6 o'clock. How far is his residence from railway station.
3)Radha, Geeta& Revathi went for a picnic. After a few days they forgot the date,day and month on which they went to picnic.Radha said that it was on Thursday,May 8 and Geeta said that it was Thursday May10.Revathi said Friday Jun 8.Now one of them told all things wrongly,others one thing wrong and the last two things wrongly. If April 1st is tuesdaywhat is the right day,date and month?

Infosys Test Paper 3

INFOSYS
PART 1
1). A beggr collects cigarette stubs and makes one ful cigarette
with every 7 stubs. Once he gets 49 stubs . How many cigarettes
can he smoke totally.
Ans. 8
2). A soldiar looses his way in a thick jungle at random walks
from his camp but mathematically in an interestingg fashion.
First he walks one mile east then half mile to north. Then 1/4
mile to west, then 1/8 mile to south and so on making a loop.
Finally hoe far he is from his camp and in which direction.
ans: in north and south directions
1/2 - 1/8 + 1/32 - 1/128 + 1/512 - and so on
= 1/2/((1-(-1/4))
similarly in east and west directions
1- 1/4 + 1/16 - 1/64 + 1/256 - and so on
= 1/(( 1- ( - 1/4))
add both the answers
3). hoe 1000000000 can be written as a product of two factors
neither of them containing zeros
Ans 2 power 9 x 5 ppower 9 ( check the answer )
4). Conversation between two mathematcians:
first : I have three childern. Thew pproduct of their ages is 36
.. If you sum their ages . it is exactly same as my neighbour's
door number on my left. The sacond mathematiciaan verfies the
door number and says that the not sufficient . Then the first
says " o.k one more clue is that my youngest is the youngest"
Immmediately the second mathematician answers . Can you aanswer
the questoion asked by the first mathematician?
What are the childeren ages? ans 2 and 3 and 6
5).. Light glows for every 13 seconds . How many times did it
between 1:57:58 and 3:20:47 am
ans : 383 + 1 = 384
6). 500 men are arranged in an array of 10 rows and 50 columns .
ALL tallest among each row aare asked to fall out . And the
shortest among THEM is A. Similarly after resuming that to their
originaal podsitions that the shorteest among each column are
asked to fall out. And the longest among them is B . Now who is
taller among A and B ?
ans A
7). A person spending out 1/3 for cloths , 1/5 of the remsaining
for food and 1/4 of the remaining for travelles is left with
Rs 100/- . How he had in the begining ?
ans RS 250/-
8). there are six boxes containing 5 , 7 , 14 , 16 , 18 , 29
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balls of either red or blue in colour. Some boxes contain only
red balls and others contain only blue . One sales man sold one
box out of them and then he says " I have the same number of red
balls left out as that of blue ". Which box is the one he solds
out ?
Ans : total no of balls = 89 and (89-29 /2 = 60/2 = 30
and also 14 + 16 = 5 + 7 + 18 = 30
9). A chain is broken into three pieces of equal lenths
conttaining 3 links each. It is taken to a backsmith to join into
a single continuous one . How many links are to tobe opened to
make it ?
Ans : 2.
10). Grass in lawn grows equally thickand in a uniform rate. It
takes 24 days for 70 cows and 60 for 30 cows . How many cows can
eat away the same in 96 days.?
Ans : 18 or 19
11). There is a certain four digit number whose fourth digit is
twise the first digit.
Third digit is three more than second digit.
Sum of the first and fourth digits twise the third number.
What was that number ?
Ans : 2034 and 4368
If you qualify in the first part then you have to appear for
the second i.e the following part.
Part 2.
1. From a vessel on the first day, 1/3rd of the liquid
evaporates. On the second day 3/4th of the remaining liquid
evaporates. what fraction of the volume is present at the end of
the II day.
2. an orange galss has orange juice. and white glass has apple
juice. Bothe equal volume 50ml of the orange juice is taken and
poured into the apple juice. 50ml from the white glass is poured
into the orange glass. Of the two quantities, the amount of
apple juice in the orange glass and the amount of orange juice in
the white glass, which one is greater and by how much?
3. there is a 4 inch cube painted on all sides. this is cut
into no of 1 inch cubes. what is the no of cubes which have no
pointed sides.
4. sam and mala have a conversation. sam says i am vertainly not
over 40. mala says i am 38 and you are atleast 5 years older
than me. Now sam says you are atleast 39. all the sattements by
the two are false. How hold are they realy.
5. ram singh goes to his office in the city, every day from his
suburban house. his driver mangaram drops him at the railway
station in the morning and picks him up in the evening. Every
evening ram singh reaches the station at 5 o'clock. mangaram
also reaches at the same time. one day ramsingh started early
from his office and came to the station at 4 o'clock. not
wanting to wait for the car he starts walking home. Mangaram
starts at normal time, picks him up on the way and takes him back
house, half an hour early. how much time did ram singh walk.
6. in a railway station, there are tow trains going. One in the
harbor line and one in the main line, each having a frequency of
10 minutes. the main line service starts at 5 o'clock. the
harbor line starts at 5.02a.m. a man goes to the station every
day to catch the first train. what is the probability of man
catching the first train
7. some people went for vaction. unfortunately it rained for 13
days when they were there. but whenever it rained in the
morning, they had clean afternood and vice versa. In all they
enjoyed 11 morning and 12 afternoons. how many days did they
stay there totally
8. exalator problem repeat
9. a survey was taken among 100 people to firn their preference
of watching t.v. programmes. there are 3 channels. given no of
people who watch
at least channel 1
" " 2
" " 3
no channels at all
atleast channels 1and 3
" " 1 and 2
" " 2 and 3
find the no of people who watched all three.
10. albert and fernandes they have two leg swimming race. both
start from opposite and of the pool. On the first leg, the boys
pass each other at 18 mt from the deep end of the pool. during
the II leg they pass at 10 mt from the shallow end of the pool.
Both go at const speed. but one of them is faster. each boy
rests for 4 sec to see at the end of the i leg. what is the
length of the pool.
11. T H I S Each alphabet stands for one
I S digit, what is the maximum value T
-------------- can take
X F X X
X X U X
--------------
X X N X X
1. an escalator is descending at constant speed. A walks down
and takes 50 steps to reach the bottom. B runs down and takes 90
steps in the same time as A takes 10 steps. how many steps are
visible when the escalator is not operating.
2. every day a cyclist meets a train at a particular crossing.
the road is straight before the crossing and both are traveling
in the same direction. cyclist travels with a speed of 10 Kmph.
One day the cyclist comes late by 25 min. and meets the train 5km
before the crossing. what is the seppd of the train.
3. five persons muckerjee, misra, iyer, patil and sharma, all
take then first or middle names in the full names. There are 4
persons having I or middle name of kumar, 3 persons with mohan, 2
persons withdev and 1 anil.
--Either mukherjee and patil have a I or middle name of dev or
misra and iyer have their I or middle name of dev
--of mukherkjee and misre, either both of them have a first or
middle name of mohan or neither have a first or middle name of
mohan
--either iyer of sharma has a I or middle name of kumar hut not
both.
who has the I or middle name of anil
4. reading comprehension
5. a bird keeper has got Pigeon, M mynas and S sparrows. the
keeper goes for lunch leaving his assistant to watch the birds.
a. suppose p=10, m=5, s=8 when the bird keeper comes back, the
assistant informs the x birds have escaped. the bird keeper
exclaims oh no! all my sparrows are gone. how many birds flew
away.
b. when the bird keeper come back, the assistand told him that
x birds have escaped. the keeper realised that atleast2 sparrows
have escaped. what is minimum no of birds that can escape.
6. select from the five alternatives A,B,C,D,E
AT THE end of each question ,two conditions will be given.
the choices are to filled at follows.
a. if a definete conclusion can be drawn from condition 1
b. if a definete conclusion can be drawn from condition 2
c. if a definete conclusion can be drawn from condition 1 and 2
d. if a definete conclusion can be drawn from condition 1 or 2
e. no conclusion can be drawn using both conditions
7. there are N coins on a table. there are two players A&B.
you can take 1 or 2 coins at a time. the person who takes the
last coin is the loser. a always starts first if N=7
a) A can always win by taking two coins in his first chanse
b) B can win only if A takes two coins in his first chance.
c) B can always win by proper play
d) none of the above
2. A can win by proper play if N is equal to
a) 13 b) 37 c) 22 d) 34 e) 48 ans. e.
3. B can win by proper play if N is equal to
a) 25 b)26 c) 32 d) 41 e) none
4. if N<4,>

Infosys Test Paper 2

--------------------------------------------------------------
1)At 6'o clock clock ticks 6 times. The time between first and
last ticks was 30sec. How much time it takes at 12'o clock.
Ans. 66 sec. 2 marks.
2)Three friends divided some bullets equally. After all of them
shot 4 bullets the total no.of remaining bullets is equal to that of
one has after division. Find the original number divided.
Ans. x x x
x-4 x-4 x-4
3x-12 = x
x= 6
ans is 18 2 marks
3)A ship went on a voyage after 180 miles a plane statrted with 10
times
speed that of the ship. Find the distance when they meet from
starting point.
Ans. 180 + (x/10) = x
x = 20
ans is 180+20=200miles. 2 marks
4) Fill the empty slots.
Three FOOTBALL teams are there. Given below the list of maches.
played won lost draw Goals for Goals against
A 2 2 *0 *0 *7 1
B 2 *0 *1 1 2 4
C 2 *0 *1 *1 3 7
the slots with stars are answers. 4 marks
BC drew with 2-2
A won on B by 2-0
a won on C by 5-1
( YOU HAVE TO FILL THE BLANKS AT APPROPRIATE STAR SYMBOLS.)`
5) There are 3 societies a,b,c. a lent tractors to b and c as many
as they had. After some time b gave as many tractors to a and c
as many as they have. After sometime c did the same thing.
At the end of this transaction each one of them had 24.
Find the tractors each orginally had.
Ans a had 39, b had 21, c had 12, 4 marks
6) There N stations on a railroad. After adding x stations 46 additional
tickets have to be printed. Find N and X.
Ans. let N(N-1) = t;
(N+x)(N+x-1) = t+46;
trail and error method x=2 and N=11 4 marks
7)Given that April 1 is tuesday. a,b,c are 3 persons told that their
farewell party was on
a - may 8, thursday
b - may 10,tuesday
c - june 8, friday
Out of a,b,c one is only correct one of the regarding month,day,date.
Other told two correct and the third person told all wrong.What is
correct date,month,day. 5 marks
(ans may be MAY 10 SUNDAY. check once again)
8)There are 4 parties. df,gs,dl(depositloss),ew ran for a contest.
Anup,Sujit,John made the following statements regarding results.
Anup said either df or ew will definitely win
sujit said he is confident that df will not win
John said he is confident that neither ew nor dl will win
the result has come. only one of the above three has made a correct
statement. Who has made the correct statement and who has won
the contest. 5 marks.
(ans DL )
9)Five people a,b,c,d,e are related to each other. Four of them make
one true statement each as follows.
i) b is my father's brother. (ans. d said this)
ii)e is my mother-in-law. ( b )
iii)c is my son-in-law's brother. ( e )
iv)a is my brother's wife. (c)
10 marks.
10) All members of d are also members of a
All '' e '' d
all '' c '' both a and b
not all '' a are members of d
not all '' d '' e
Some questions on these conditions.(5questions 5 marks)
11)boys are allowed to watch football at c.v.Raman auditorium subjected to conditions.
i)the boy over age 16 can wear overcoat
ii)no boy over age 15 can wear cap
iii)to watch the football either he has to wear overcoat or cap
or both
iv) a boy with an umberella or above 16 or both cannot wear sweater
v) boys must either not watch football or wear sweater.
What is the appearence of the boy who is watching football.
Try to solve this question.................
YOU HAVE TO DO SOME ROUGH WORK FOR EACH QUESTION . IT WILL
CARRY SOME GRACE MARKS.

problem1
-----------------
halley is clarks father&arthur is halleys father.after some years when
halleys age is equal to arthurs age,halleys age becomes 5 times of
clarks
present age.clarks age then is 8 times his fathers present age.
sum of arthur & halleys age is 100
find clarks present age;;;;;;;;;;;;;;;;;;;;; (2 marks)
problem2(3-marks)
---------------------------
substraction--------
(there were some blank spaces left)
answer 1 2 1 2 6
- 5 4 6 3
-------------
5 6 6 3
problem no. 3(4-marks)
there are two glasses, one is filled with orange juice and other is
filled with apple juice both in equal quantities say 50 50 ml. 50%
orange juice is poured in apple juice and than the 50% mixture of
orange and apple juice is poured in the glass of orang
e juice. Now you have to find out how much orange juice is there in
apple juice glass and vice-versa. (3)
answer-------equal amount
problem no 4(5-7 marks)
There are three tribes Pokka (always tells true), Wokka (always tells
lie), and Solla (alternately tells true/lies (say for example
true-false true or false-true-false)). There are three persons
Add, even, divide and there are s
ome statements given by the persons. The statements are as
follows.
Add says--
1. My house no. is divisible by 4.
2. " second statement don't remember".
3. The difference between each of these houses is 13.
Even says--

1. Add's house no is divisible by 12.
2. My house no. is 37.
3. "third statement don't remember".
Divide says--
1. Add's house no. is divisible by 3.
2. My house no is 30.
3. No one's house no. is divisible by 10.
Their house no.s are in the range of 1 to 50. Now you
have to rmine, these three persons belong to which
category of tribes You also have to tell their house no.
answers are----
Add-------->Wotta--------->Lies--------->house no. ?
Even-------->Pokka-------->True---------> ?
Divide------>Solla-------->alternate----> ?
problem 5(4-marks)
------------
there are two boats across a river.one of the boat starts
from x and proceeds to y at the other river end.while the other
boat starts from y and proceeds to x.the first time these two
boats meet is 200 kms from x.they continue their journey
reach y and x respectively.
when they come back they meet at a point
which is 400 kms from y .find the width of the river ..
(the figures aren't precise but this is a simple problem)
problem6(8-marks)
-----------
there are 2 twins--the 1st twin speaks the truth on mon,
wed,fri and lies on tue,thu,sat.while the 2nd twin speaks truth on tue
thu,sat and lies on mon,wed,fri.Both of them speak the truth on
sunday.
there are 4 sub-questions
a) 1st twin: yesterday was sunday
2nd twin:yes you are speaking the truth
alternatives:
A-TODAY IS MONDAY
B-TODAY IS SATURDAY
C-1ST TWIN IS SPEAKING THE TRUTH
D-ETC......
i can remember only the 1st bit .there are 3 more
problem7(7-marks)

2 families jones and smith.jones family has 4 children
smiths family has 3 children.one family has 2 twins
----there were some conds. given.u have to tell the
members of each family-and their ages....
my friend could recollect the answers verbatim
answers
----
jones ages smith ages
------- --------
d- 10 h- 15
d- 10 b- 13
w- 8 b- 11
remainig one --
------------------------------------------------------------
the names are lengthy--d-,w-h-b- are all their names first
letters---find the exact names in the q papers

Infosys Test Paper 1

PAPER CODE Q/C.
----------------------------------------------------------------------
1a) BE * BE = ACB
A,B,C,E ARE NON ZERO NUMBERS FIND B,E.
ANS) B=1 E=9
2) A,B,C,D,E ARE HAVING NUMERICAL VALUES. THERE ARE SOME CONDITIONS
GIVEN
a) A=C <===> B!=E
b) DIFFERENCE BETWEEN A AND C AS SAME AS DIFFERENCE BETWEEN C AND B
AS SAME AS DIFFERENCE BETWEEN A AND D
c) CD
THEN FIND A,B,C,D,E
3) THERE ARE SIX CARDS IN WHICH IT HAS TWO KING CARDS. ALL CARDS ARE
TURNED DOWN AND TWO CARDS ARE OPENED
a) WHAT IS THE POSSOBILITY TO GET AT LEAST ONE KING.
b) WHAT IS THE POSSIBILITY TO GET TWO KINGS.
4) A PERSON WENT TO A SHOP AND ASKED FOR CHANGE FOR 1.15PAISE.
BUT HE SAID THAT HE COULD NOT ONLY GIVE CHANGE FOR ONE RUPEE.
BUT ALSO FOR 50P,25P,10P AND 5P. WHAT WERE THE COINS HE HAD
ans) 1-->50 4--->10P 1--->25P
5) THERE ARE 3 NURSES AND THEY WORK ALTOGETHER ONLY ONCE IN A WEEK.
NO NURSE IS CALLED TO WORK FOR 3 CONSECUTIVE DAYS.
NURSE 1 IS OFF ON TUESEDAY,THURSDAY AND SUNDAY.
NURSE 2 IS OFF ON SATURDAY.
NURSE 3 IS OFF ON THURSDAY,SUNDAY.
NO TWO NURSES ARE OFF MORE THAN ONCE A WEEK.
FIND THE DAY ON WHICH ALL THE 3 NURSES WERE ON WORK.
6) THERE ARE 5 PERSONS A,B,C,D,E AND EACH IS WEARING A BLOCK OR WHITE
CAP ON HIS HEAD. A PERSON CAN SEE THE CAPS OF THE REMAINING 4 BUT CAN'T SEE HIS OWN CAP. A PERSON WEARING WHITE SAYS TRUE AND WHO WEARS BLOCK SAYS FALSE.
i) A SAYS I SEE 3 WHITES AND 1 BLOCK
ii) B SAYS I SEE 4 BLOCKS
iii) E SAYS I SEE 4 WHITES
iiii) C SAYS I SEE 3 BLOCKS AND 1 WHITE.
NOW FIND THE CAPS WEARED BY A,B,C,D AND E
Answer : Black, Black, White, White, Black
7) THERE ARE TWO WOMEN, KAVITHA AND SHAMILI AND TWO MALES SHYAM,
ARAVIND
WHO ARE MUSICIANS. OUT OF THESE FOUR ONE IS A PIANIST, ONE FLUTIST,
VIOLINIST AND DRUMMER.
i) ACROSS ARAVIND BEATS PIANIST
ii) ACROSS SHYAM IS NOT A FLUTIST
iii) KAVITHA'S LEFT IS A PIANIST
iiii) SHAMILI'S LEFT IS NOT A DRUMMER
V) FLUTIST AND DRUMMER ARE MARRIED.
8) 1/3 ED OF THE CONTENTS OF A CONTAINER EVAPORATED ON THE 1 ST DAY.
3/4 TH OF THE REMAINING CONTENTS OF THE CONTAINER EVAPORATED THE
SECOND DAY. WHAT PART OF THE CONTENTS OF THE CONTAINER ARE LEFT AT
THE END OF THE SECOND DAY. Answer : 1/6
9) A MAN COVERED 28 STEPS IN 30 SECONDS BUT HE DECIDED TO MOVE FAST AN
D
COVERED 34 STEPS IN 18 SECONDS. HOW MANY STEPS ARE THERE ON THE
ESCALATOR WHEN STATIONARY. Answer : 43
10) ALL FAIR SKINNED, RICH, HANDSOME, MUSCULAR, LEAN AND EMPLOYED ARE
TALL MEN
1) ALL LEAN MEN ARE MUSCULAR.
2) NO FAIRSKINNED PERSON WHO IS NOT RICH IS HANDSOME.
3) SOME MUSCULAR MEN ARE HANDSOME.
4) ALL HANDSOME ARE FAIRSKINNED.
5) NO PERSON WHO IS NEITHER FAIR SKINNED NOR MUSCULAR IS ENPLYED.
6) we unable to recall this condition and question also incomplete

Operating System Questions

Following are a few basic questions that cover the essentials of OS:

1. What is the difference between Swapping and Paging?

Swapping: Whole process is moved from the swap device to the main memory for execution.Process size must be less than or equal to the available main memory.It is easier to implementation and overhead to the system.Swapping system does not handle the memory more flexibly as compated to the paging systems.
Paging:Only the required memory pages are moved to main memory from the swap device for execution. Process size does not matter. Gives the concept of the virtual memory.

It provides greater flexibility in mapping the virtual address space into the physical memory of the machine. Allows more number of processes to fit in the main memory simultaneously. Allows the greater process size than the available physical memory. Demand paging systems handle the memory more flexibly.

2. What is major difference between the Historic Unix and the new BSD release of Unix System V in terms of Memory Management?

Historic Unix uses Swapping - entire process is transferred to the main memory from the swap device, whereas the Unix System V uses Demand Paging - only the part of the process is moved to the main memory. Historic Unix uses one Swap Device and Unix System V allow multiple Swap Devices.

3. What is the main goal of the Memory Management?

· It decides which process should reside in the main memory,

· Manages the parts of the virtual address space of a process which is non-core resident,

· Monitors the available main memory and periodically write the processes into the swap device to provide more processes fit in the main memory simultaneously.

4. What is a Map?

A Map is an Array, which contains the addresses of the free space in the swap device that are allocatable resources, and the number of the resource units available there.

This allows First-Fit allocation of contiguous blocks of a resource. Initially the Map contains one entry - address (block offset from the starting of the swap area) and the total number of resources.

Kernel treats each unit of Map as a group of disk blocks. On the allocation and freeing of the resources Kernel updates the Map for accurate information.

5. What scheme does the Kernel in Unix System V follow while choosing a swap device among the multiple swap devices?

Kernel follows Round Robin scheme choosing a swap device among the multiple swap devices in Unix System V.

6. What is a Region?

A Region is a continuous area of a process’s address space (such as text, data and stack). The kernel in a ‘Region Table’ that is local to the process maintains region. Regions are sharable among the process.

7. What are the events done by the Kernel after a process is being swapped out from the main memory?

When Kernel swaps the process out of the primary memory, it performs the following:

Ø Kernel decrements the Reference Count of each region of the process. If the reference count becomes zero, swaps the region out of the main memory,

Ø Kernel allocates the space for the swapping process in the swap device,

Ø Kernel locks the other swapping process while the current swapping operation is going on,

Ø The Kernel saves the swap address of the region in the region table.

8. Is the Process before and after the swap are the same? Give reason.

Process before swapping is residing in the primary memory in its original form. The regions (text, data and stack) may not be occupied fully by the process, there may be few empty slots in any of the regions and while swapping Kernel do not bother about the empty slots while swapping the process out.

After swapping the process resides in the swap (secondary memory) device. The regions swapped out will be present but only the occupied region slots but not the empty slots that were present before assigning.

While swapping the process once again into the main memory, the Kernel referring to the Process Memory Map, it assigns the main memory accordingly taking care of the empty slots in the regions.

9. What do you mean by u-area (user area) or u-block?

This contains the private data that is manipulated only by the Kernel. This is local to the Process, i.e. each process is allocated a u-area.

10. What are the entities that are swapped out of the main memory while swapping the process out of the main memory?

All memory space occupied by the process, process’s u-area, and Kernel stack are swapped out, theoretically.

Practically, if the process’s u-area contains the Address Translation Tables for the process then Kernel implementations do not swap the u-area.

11. What is Fork swap?

fork() is a system call to create a child process. When the parent process calls fork() system call, the child process is created and if there is short of memory then the child process is sent to the read-to-run state in the swap device, and return to the user state without swapping the parent process. When the memory will be available the child process will be swapped into the main memory.

12. What is Expansion swap?

At the time when any process requires more memory than it is currently allocated, the Kernel performs Expansion swap. To do this Kernel reserves enough space in the swap device. Then the address translation mapping is adjusted for the new virtual address space but the physical memory is not allocated. At last Kernel swaps the process into the assigned space in the swap device. Later when the Kernel swaps the process into the main memory this assigns memory according to the new address translation mapping.

13. How the Swapper works?

The swapper is the only process that swaps the processes. The Swapper operates only in the Kernel mode and it does not uses System calls instead it uses internal Kernel functions for swapping. It is the archetype of all kernel process.

14. What are the processes that are not bothered by the swapper? Give Reason.

Ø Zombie process: They do not take any up physical memory.

Ø Processes locked in memories that are updating the region of the process.

Ø Kernel swaps only the sleeping processes rather than the ‘ready-to-run’ processes, as they have the higher probability of being scheduled than the Sleeping processes.

15. What are the requirements for a swapper to work?

The swapper works on the highest scheduling priority. Firstly it will look for any sleeping process, if not found then it will look for the ready-to-run process for swapping. But the major requirement for the swapper to work the ready-to-run process must be core-resident for at least 2 seconds before swapping out. And for swapping in the process must have been resided in the swap device for at least 2 seconds. If the requirement is not satisfied then the swapper will go into the wait state on that event and it is awaken once in a second by the Kernel.

16. What are the criteria for choosing a process for swapping into memory from the swap device?

The resident time of the processes in the swap device, the priority of the processes and the amount of time the processes had been swapped out.

17. What are the criteria for choosing a process for swapping out of the memory to the swap device?

Ø The process’s memory resident time,

Ø Priority of the process and

Ø The nice value.

18. What do you mean by nice value?

Nice value is the value that controls {increments or decrements} the priority of the process. This value that is returned by the nice () system call. The equation for using nice value is:

Priority = (“recent CPU usage”/constant) + (base- priority) + (nice value)

Only the administrator can supply the nice value. The nice () system call works for the running process only. Nice value of one process cannot affect the nice value of the other process.

19. What are conditions on which deadlock can occur while swapping the processes?

· All processes in the main memory are asleep.

· All ‘ready-to-run’ processes are swapped out.

· There is no space in the swap device for the new incoming process that are swapped out of the main memory.

· There is no space in the main memory for the new incoming process.

20. What are conditions for a machine to support Demand Paging?

· Memory architecture must based on Pages,

· The machine must support the ‘restartable’ instructions.

21. What is ‘the principle of locality’?

It’s the nature of the processes that they refer only to the small subset of the total data space of the process. i.e. the process frequently calls the same subroutines or executes the loop instructions.

22. What is the working set of a process?

The set of pages that are referred by the process in the last ‘n’, references, where ‘n’ is called the window of the working set of the process.

23. What is the window of the working set of a process?

The window of the working set of a process is the total number in which the process had referred the set of pages in the working set of the process.

24. What is called a page fault?

Page fault is referred to the situation when the process addresses a page in the working set of the process but the process fails to locate the page in the working set. And on a page fault the kernel updates the working set by reading the page from the secondary device.

25. What are data structures that are used for Demand Paging?

Kernel contains 4 data structures for Demand paging. They are,

Ø Page table entries,

Ø Disk block descriptors,

Ø Page frame data table (pfdata),

Ø Swap-use table.

What are the bits that support the demand paging?

Valid, Reference, Modify, Copy on write, Age. These bits are the part of the page table entry, which includes physical address of the page and protection bits.

Page address AgeCopy on writeModifyReferenceValidProtection

How the Kernel handles the fork() system call in traditional Unix and in the System V Unix, while swapping?

Kernel in traditional Unix, makes the duplicate copy of the parent’s address space and attaches it to the child’s process, while swapping. Kernel in System V Unix, manipulates the region tables, page table, and pfdata table entries, by incrementing the reference count of the region table of shared regions.

Difference between the fork() and vfork() system call?

During the fork() system call the Kernel makes a copy of the parent process’s address space and attaches it to the child process.

But the vfork() system call do not makes any copy of the parent’s address space, so it is faster than the fork() system call. The child process as a result of the vfork() system call executes exec() system call. The child process from vfork() system call executes in the parent’s address space (this can overwrite the parent’s data and stack ) which suspends the parent process until the child process exits.

What is BSS(Block Started by Symbol)?

A data representation at the machine level, that has initial values when a program starts and tells about how much space the kernel allocates for the un-initialized data. Kernel initializes it to zero at run-time.

What is Page-Stealer process?

This is the Kernel process that makes rooms for the incoming pages, by swapping the memory pages that are not the part of the working set of a process. Page-Stealer is created by the Kernel at the system initialization and invokes it throughout the lifetime of the system. Kernel locks a region when a process faults on a page in the region, so that page stealer cannot steal the page, which is being faulted in.

Name two paging states for a page in memory?

The two paging states are:

· The page is aging and is not yet eligible for swapping,

· The page is eligible for swapping but not yet eligible for reassignment to other virtual address space.

What are the phases of swapping a page from the memory?

· Page stealer finds the page eligible for swapping and places the page number in the list of pages to be swapped.

· Kernel copies the page to a swap device when necessary and clears the valid bit in the page table entry, decrements the pfdata reference count, and places the pfdata table entry at the end of the free list if its reference count is 0.

What is page fault? Its types?

Page fault refers to the situation of not having a page in the main memory when any process references it.

There are two types of page fault :

· Validity fault,

· Protection fault.

In what way the Fault Handlers and the Interrupt handlers are different?

Fault handlers are also an interrupt handler with an exception that the interrupt handlers cannot sleep. Fault handlers sleep in the context of the process that caused the memory fault. The fault refers to the running process and no arbitrary processes are put to sleep.

What is validity fault?

If a process referring a page in the main memory whose valid bit is not set, it results in validity fault.

The valid bit is not set for those pages:

· that are outside the virtual address space of a process,

· that are the part of the virtual address space of the process but no physical address is assigned to it.

What does the swapping system do if it identifies the illegal page for swapping?

If the disk block descriptor does not contain any record of the faulted page, then this causes the attempted memory reference is invalid and the kernel sends a “Segmentation violation” signal to the offending process. This happens when the swapping system identifies any invalid memory reference.

What are states that the page can be in, after causing a page fault?

· On a swap device and not in memory,

· On the free page list in the main memory,

· In an executable file,

· Marked “demand zero”,

· Marked “demand fill”.

In what way the validity fault handler concludes?

· It sets the valid bit of the page by clearing the modify bit.

· It recalculates the process priority.

At what mode the fault handler executes?

At the Kernel Mode.

What do you mean by the protection fault?

Protection fault refers to the process accessing the pages, which do not have the access permission. A process also incur the protection fault when it attempts to write a page whose copy on write bit was set during the fork() system call.

How the Kernel handles the copy on write bit of a page, when the bit is set?

In situations like, where the copy on write bit of a page is set and that page is shared by more than one process, the Kernel allocates new page and copies the content to the new page and the other processes retain their references to the old page. After copying the Kernel updates the page table entry with the new page number. Then Kernel decrements the reference count of the old pfdata table entry.

In cases like, where the copy on write bit is set and no processes are sharing the page, the Kernel allows the physical page to be reused by the processes. By doing so, it clears the copy on write bit and disassociates the page from its disk copy (if one exists), because other process may share the disk copy. Then it removes the pfdata table entry from the page-queue as the new copy of the virtual page is not on the swap device. It decrements the swap-use count for the page and if count drops to 0, frees the swap space.

For which kind of fault the page is checked first?

The page is first checked for the validity fault, as soon as it is found that the page is invalid (valid bit is clear), the validity fault handler returns immediately, and the process incur the validity page fault. Kernel handles the validity fault and the process will incur the protection fault if any one is present.

In what way the protection fault handler concludes?

After finishing the execution of the fault handler, it sets the modify and protection bits and clears the copy on write bit. It recalculates the process-priority and checks for signals.

How the Kernel handles both the page stealer and the fault handler?

The page stealer and the fault handler thrash because of the shortage of the memory. If the sum of the working sets of all processes is greater that the physical memory then the fault handler will usually sleep because it cannot allocate pages for a process. This results in the reduction of the system throughput because Kernel spends too much time in overhead, rearranging the memory in the frantic pace.

Explain the concept of Reentrancy.

It is a useful, memory-saving technique for multiprogrammed timesharing systems. A Reentrant Procedure is one in which multiple users can share a single copy of a program during the same period. Reentrancy has 2 key aspects: The program code cannot modify itself, and the local data for each user process must be stored separately. Thus, the permanent part is the code, and the temporary part is the pointer back to the calling program and local variables used by that program. Each execution instance is called activation. It executes the code in the permanent part, but has its own copy of local variables/parameters. The temporary part associated with each activation is the activation record. Generally, the activation record is kept on the stack.

Note: A reentrant procedure can be interrupted and called by an interrupting program, and still execute correctly on returning to the procedure.

Explain Belady's Anomaly.

Also called FIFO anomaly. Usually, on increasing the number of frames allocated to a process' virtual memory, the process execution is faster, because fewer page faults occur. Sometimes, the reverse happens, i.e., the execution time increases even when more frames are allocated to the process. This is Belady's Anomaly. This is true for certain page reference patterns.

What is a binary semaphore? What is its use?

A binary semaphore is one, which takes only 0 and 1 as values. They are used to implement mutual exclusion and synchronize concurrent processes.

What is thrashing?

It is a phenomenon in virtual memory schemes when the processor spends most of its time swapping pages, rather than executing instructions. This is due to an inordinate number of page faults.

List the Coffman's conditions that lead to a deadlock.

· Mutual Exclusion: Only one process may use a critical resource at a time.

· Hold & Wait: A process may be allocated some resources while waiting for others.

· No Pre-emption: No resource can be forcible removed from a process holding it.

· Circular Wait: A closed chain of processes exist such that each process holds at least one resource needed by another process in the chain.

What are short-, long- and medium-term scheduling?

Long term scheduler determines which programs are admitted to the system for processing. It controls the degree of multiprogramming. Once admitted, a job becomes a process.

Medium term scheduling is part of the swapping function. This relates to processes that are in a blocked or suspended state. They are swapped out of real-memory until they are ready to execute. The swapping-in decision is based on memory-management criteria.

Short term scheduler, also know as a dispatcher executes most frequently, and makes the finest-grained decision of which process should execute next. This scheduler is invoked whenever an event occurs. It may lead to interruption of one process by preemption.

What are turnaround time and response time?

Turnaround time is the interval between the submission of a job and its completion. Response time is the interval between submission of a request, and the first response to that request.

What are the typical elements of a process image?

· User data: Modifiable part of user space. May include program data, user stack area, and programs that may be modified.

· User program: The instructions to be executed.

· System Stack: Each process has one or more LIFO stacks associated with it. Used to store parameters and calling addresses for procedure and system calls.

· Process control Block (PCB): Info needed by the OS to control processes.

What is the Translation Lookaside Buffer (TLB)?

In a cached system, the base addresses of the last few referenced pages is maintained in registers called the TLB that aids in faster lookup. TLB contains those page-table entries that have been most recently used. Normally, each virtual memory reference causes 2 physical memory accesses-- one to fetch appropriate page-table entry, and one to fetch the desired data. Using TLB in-between, this is reduced to just one physical memory access in cases of TLB-hit.

What is the resident set and working set of a process?

Resident set is that portion of the process image that is actually in real-memory at a particular instant. Working set is that subset of resident set that is actually needed for execution. (Relate this to the variable-window size method for swapping techniques.)

When is a system in safe state?

The set of dispatchable processes is in a safe state if there exists at least one temporal order in which all processes can be run to completion without resulting in a deadlock.

What is cycle stealing?

We encounter cycle stealing in the context of Direct Memory Access (DMA). Either the DMA controller can use the data bus when the CPU does not need it, or it may force the CPU to temporarily suspend operation. The latter technique is called cycle stealing. Note that cycle stealing can be done only at specific break points in an instruction cycle.

What is meant by arm-stickiness?

If one or a few processes have a high access rate to data on one track of a storage disk, then they may monopolize the device by repeated requests to that track. This generally happens with most common device scheduling algorithms (LIFO, SSTF, C-SCAN, etc). High-density multisurface disks are more likely to be affected by this than low density ones.

What are the stipulations of C2 level security?

C2 level security provides for:

· Discretionary Access Control

· Identification and Authentication

· Auditing

· Resource reuse

What is busy waiting?

The repeated execution of a loop of code while waiting for an event to occur is called busy-waiting. The CPU is not engaged in any real productive activity during this period, and the process does not progress toward completion.

Explain the popular multiprocessor thread-scheduling strategies.

· Load Sharing: Processes are not assigned to a particular processor. A global queue of threads is maintained. Each processor, when idle, selects a thread from this queue. Note that load balancing refers to a scheme where work is allocated to processors on a more permanent basis.

· Gang Scheduling: A set of related threads is scheduled to run on a set of processors at the same time, on a 1-to-1 basis. Closely related threads / processes may be scheduled this way to reduce synchronization blocking, and minimize process switching. Group scheduling predated this strategy.

· Dedicated processor assignment: Provides implicit scheduling defined by assignment of threads to processors. For the duration of program execution, each program is allocated a set of processors equal in number to the number of threads in the program. Processors are chosen from the available pool.

· Dynamic scheduling: The number of thread in a program can be altered during the course of execution.

When does the condition 'rendezvous' arise?

In message passing, it is the condition in which, both, the sender and receiver are blocked until the message is delivered.

What is a trap and trapdoor?

Trapdoor is a secret undocumented entry point into a program used to grant access without normal methods of access authentication. A trap is a software interrupt, usually the result of an error condition.

What are local and global page replacements?

Local replacement means that an incoming page is brought in only to the relevant process' address space. Global replacement policy allows any page frame from any process to be replaced. The latter is applicable to variable partitions model only.

Define latency, transfer and seek time with respect to disk I/O.

Seek time is the time required to move the disk arm to the required track. Rotational delay or latency is the time it takes for the beginning of the required sector to reach the head. Sum of seek time (if any) and latency is the access time. Time taken to actually transfer a span of data is transfer time.

Describe the Buddy system of memory allocation.

Free memory is maintained in linked lists, each of equal sized blocks. Any such block is of size 2^k. When some memory is required by a process, the block size of next higher order is chosen, and broken into two. Note that the two such pieces differ in address only in their kth bit. Such pieces are called buddies. When any used block is freed, the OS checks to see if its buddy is also free. If so, it is rejoined, and put into the original free-block linked-list.

What is time-stamping?

It is a technique proposed by Lamport, used to order events in a distributed system without the use of clocks. This scheme is intended to order events consisting of the transmission of messages. Each system 'i' in the network maintains a counter Ci. Every time a system transmits a message, it increments its counter by 1 and attaches the time-stamp Ti to the message. When a message is received, the receiving system 'j' sets its counter Cj to 1 more than the maximum of its current value and the incoming time-stamp Ti. At each site, the ordering of messages is determined by the following rules: For messages x from site i and y from site j, x precedes y if one of the following conditions holds....(a) if Ti (b) if Ti=Tj and i

How are the wait/signal operations for monitor different from those for semaphores?

If a process in a monitor signal and no task is waiting on the condition variable, the signal is lost. So this allows easier program design. Whereas in semaphores, every operation affects the value of the semaphore, so the wait and signal operations should be perfectly balanced in the program.

In the context of memory management, what are placement and replacement algorithms?

Placement algorithms determine where in available real-memory to load a program. Common methods are first-fit, next-fit, best-fit. Replacement algorithms are used when memory is full, and one process (or part of a process) needs to be swapped out to accommodate a new program. The replacement algorithm determines which are the partitions to be swapped out.

In loading programs into memory, what is the difference between load-time dynamic linking and run-time dynamic linking?

For load-time dynamic linking: Load module to be loaded is read into memory. Any reference to a target external module causes that module to be loaded and the references are updated to a relative address from the start base address of the application module.

With run-time dynamic loading: Some of the linking is postponed until actual reference during execution. Then the correct module is loaded and linked.

What are demand- and pre-paging?

With demand paging, a page is brought into memory only when a location on that page is actually referenced during execution. With pre-paging, pages other than the one demanded by a page fault are brought in. The selection of such pages is done based on common access patterns, especially for secondary memory devices.

Paging a memory management function, while multiprogramming a processor management function, are the two interdependent?

Yes.

What is page cannibalizing?

Page swapping or page replacements are called page cannibalizing.

What has triggered the need for multitasking in PCs?

· Increased speed and memory capacity of microprocessors together with the support fir virtual memory and

· Growth of client server computing

What are the four layers that Windows NT have in order to achieve independence?

· Hardware abstraction layer

· Kernel

· Subsystems

· System Services.

What is SMP?

To achieve maximum efficiency and reliability a mode of operation known as symmetric multiprocessing is used. In essence, with SMP any process or threads can be assigned to any processor.

What are the key object oriented concepts used by Windows NT?

· Encapsulation

· Object class and instance

Is Windows NT a full blown object oriented operating system? Give reasons.

No Windows NT is not so, because its not implemented in object oriented language and the data structures reside within one executive component and are not represented as objects and it does not support object oriented capabilities .

What is a drawback of MVT?

It does not have the features like

· ability to support multiple processors

· virtual storage

· source level debugging

What is process spawning?

When the OS at the explicit request of another process creates a process, this action is called process spawning.

How many jobs can be run concurrently on MVT?

15 jobs

List out some reasons for process termination.

· Normal completion

· Time limit exceeded

· Memory unavailable

· Bounds violation

· Protection error

· Arithmetic error

· Time overrun

· I/O failure

· Invalid instruction

· Privileged instruction

· Data misuse

· Operator or OS intervention

· Parent termination.

What are the reasons for process suspension?

· swapping

· interactive user request

· timing

· parent process request

What is process migration?

It is the transfer of sufficient amount of the state of process from one machine to the target machine

What is mutant?

In Windows NT a mutant provides kernel mode or user mode mutual exclusion with the notion of ownership.

What is an idle thread?

The special thread a dispatcher will execute when no ready thread is found.

What is FtDisk?

It is a fault tolerance disk driver for Windows NT.

What are the possible threads a thread can have?

· Ready

· Standby

· Running

· Waiting

· Transition

· Terminated.

What are rings in Windows NT?

Windows NT uses protection mechanism called rings provides by the process to implement separation between the user mode and kernel mode.

What is Executive in Windows NT?

In Windows NT, executive refers to the operating system code that runs in kernel mode.

What are the sub-components of I/O manager in Windows NT?

· Network redirector/ Server

· Cache manager.

· File systems

· Network driver

· Device driver

What are DDks? Name an operating system that includes this feature.

DDks are device driver kits, which are equivalent to SDKs for writing device drivers. Windows NT includes DDks.

What level of security does Windows NT meets?

C2 level security.