GATE CS 2018: Computer Science and Information Technology
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GATE 2018 General Aptitude (GA) Set-3
Q. 1 – Q. 5 carry one mark each.
Q.1 “From where are they bringing their books? ________ bringing _______ books from
_____.”
The words that best fill the blanks in the above sentence are
(A) Their, they’re, there
(B) They’re, their, there
(C) There, their, they’re
(D) They’re, there, there
Q.2 “A _________ investigation can sometimes yield new facts, but typically organized ones
are more successful.”
The word that best fills the blank in the above sentence is
(A) meandering (B) timely (C) consistent (D) systematic
Q.3 The area of a square is d. What is the area of the circle which has the diagonal of the
square as its diameter?
1 1
(A) πd (B) πd 2 (C) πd 2 (D) πd
4 2
Q.4 What would be the smallest natural number which when divided either by 20 or by 42 or
by 76 leaves a remainder of 7 in each case?
(A) 3047 (B) 6047 (C) 7987 (D) 63847
Q.5 What is the missing number in the following sequence?
2, 12, 60, 240, 720, 1440, _____, 0
(A) 2880 (B) 1440 (C) 720 (D) 0
GA 1/3
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GATE 2018 General Aptitude (GA) Set-3
Q. 6 – Q. 10 carry two marks each.
Q.6 In appreciation of the social improvements completed in a town, a wealthy philanthropist
decided to gift Rs 750 to each male senior citizen in the town and Rs 1000 to each female
senior citizen. Altogether, there were 300 senior citizens eligible for this gift. However,
only 8/9th of the eligible men and 2/3rd of the eligible women claimed the gift. How much
money (in Rupees) did the philanthropist give away in total?
(A) 1,50,000 (B) 2,00,000
(C) 1,75,000 (D) 1,51,000
1 1 1
Q.7 If pqr ≠ 0 and p−x = , q −y = , r −z = , what is the value of the product xyz?
q r p
(A) −1 1 (C) 1 (D) pqr
(B)
pqr
Q.8 In a party, 60% of the invited guests are male and 40% are female. If 80% of the invited
guests attended the party and if all the invited female guests attended, what would be the
ratio of males to females among the attendees in the party?
(A) 2:3 (B) 1:1 (C) 3:2 (D) 2:1
Q.9 In the figure below, ∠DEC + ∠BFC is equal to ____________ .
E
D C
F
B
A
(A) ∠BCD − ∠BAD (B) ∠BAD + ∠BCF
(C) ∠BAD + ∠BCD (D) ∠CBA + ∠ADC
GA 2/3
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GATE 2018 General Aptitude (GA) Set-3
Q.10 A six sided unbiased die with four green faces and two red faces is rolled seven times.
Which of the following combinations is the most likely outcome of the experiment?
(A) Three green faces and four red faces.
(B) Four green faces and three red faces.
(C) Five green faces and two red faces.
(D) Six green faces and one red face.
END OF THE QUESTION PAPER
GA 3/3
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q. 1 – Q. 25 carry one mark each.
Q.1 Which one of the following is a closed form expression for the generating function of the
sequence {an}, where an = 2n + 3 for all n = 0, 1, 2,… ?
3 3x 2 x 3 x
(A) (B) (C) (D)
(1 x)2 (1 x)2 (1 x)2 (1 x)2
Q.2 Consider the following C program.
#include<stdio.h>
struct Ournode{
char x,y,z;
};
int main(){
struct Ournode p = {'1', '0', 'a'+2};
struct Ournode *q = &p;
printf ("%c, %c", *((char*)q+1), *((char*)q+2));
return 0;
}
The output of this program is:
(A) 0, c (B) 0, a+2 (C) '0', 'a+2' (D) '0', 'c'
Q.3 A queue is implemented using a non-circular singly linked list. The queue has a head pointer
and a tail pointer, as shown in the figure. Let n denote the number of nodes in the queue. Let
enqueue be implemented by inserting a new node at the head, and dequeue be
implemented by deletion of a node from the tail.
head tail
Which one of the following is the time complexity of the most time-efficient implementation
of enqueue and dequeue, respectively, for this data structure?
(A) θ(1), θ(1) (B) θ(1), θ(n) (C) θ(n), θ(1) (D) θ(n), θ(n)
CS 1/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.4 Let ⊕ and ⊙ denote the Exclusive OR and Exclusive NOR operations, respectively.
Which one of the following is NOT CORRECT?
(A) ̅̅̅̅̅̅̅̅
P⊕Q =P⊙Q
(B) P̅ ⊕ Q = P ⊙ Q
(C) P̅ ⊕ Q̅ = P ⊕ Q
(D) (P ⊕ P̅) ⊕ Q = (P ⊙ P̅ ) ⊙ Q̅
Q.5 Consider the following processor design characteristics.
I. Register-to-register arithmetic operations only
II. Fixed-length instruction format
III. Hardwired control unit
Which of the characteristics above are used in the design of a RISC processor?
(A) I and II only (B) II and III only (C) I and III only (D) I, II and III
Q.6 Let N be an NFA with n states. Let k be the number of states of a minimal DFA which is
equivalent to N. Which one of the following is necessarily true?
(A) k ≥ 2n (B) k ≥ n (C) k ≤ n2 (D) k ≤ 2n
Q.7 The set of all recursively enumerable languages is
(A) closed under complementation.
(B) closed under intersection.
(C) a subset of the set of all recursive languages.
(D) an uncountable set.
Q.8 Which one of the following statements is FALSE?
(A) Context-free grammar can be used to specify both lexical and syntax rules.
(B) Type checking is done before parsing.
(C) High-level language programs can be translated to different Intermediate
Representations.
(D) Arguments to a function can be passed using the program stack.
CS 2/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.9 The following are some events that occur after a device controller issues an interrupt while
process L is under execution.
(P) The processor pushes the process status of L onto the control stack.
(Q) The processor finishes the execution of the current instruction.
(R) The processor executes the interrupt service routine.
(S) The processor pops the process status of L from the control stack.
(T) The processor loads the new PC value based on the interrupt.
Which one of the following is the correct order in which the events above occur?
(A) QPTRS (B) PTRSQ (C) TRPQS (D) QTPRS
Q.10 Consider a process executing on an operating system that uses demand paging. The average
time for a memory access in the system is M units if the corresponding memory page is
available in memory, and D units if the memory access causes a page fault. It has been
experimentally measured that the average time taken for a memory access in the process is
X units.
Which one of the following is the correct expression for the page fault rate experienced by
the process?
(A) (D – M) / (X – M) (B) (X – M) / (D – M)
(C) (D – X) / (D – M) (D) (X – M) / (D – X)
Q.11 In an Entity-Relationship (ER) model, suppose R is a many-to-one relationship from entity
set E1 to entity set E2. Assume that E1 and E2 participate totally in R and that the cardinality
of E1 is greater than the cardinality of E2.
Which one of the following is true about R?
(A) Every entity in E1 is associated with exactly one entity in E2.
(B) Some entity in E1 is associated with more than one entity in E2.
(C) Every entity in E2 is associated with exactly one entity in E1.
(D) Every entity in E2 is associated with at most one entity in E1.
CS 3/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.12 Consider the following two tables and four queries in SQL.
Book (isbn, bname), Stock (isbn, copies)
Query 1: SELECT B.isbn, S.copies
FROM Book B INNER JOIN Stock S
ON B.isbn = S.isbn;
Query 2: SELECT B.isbn, S.copies
FROM Book B LEFT OUTER JOIN Stock S
ON B.isbn = S.isbn;
Query 3: SELECT B.isbn, S.copies
FROM Book B RIGHT OUTER JOIN Stock S
ON B.isbn = S.isbn;
Query 4: SELECT B.isbn, S.copies
FROM Book B FULL OUTER JOIN Stock S
ON B.isbn = S.isbn;
Which one of the queries above is certain to have an output that is a superset of the outputs
of the other three queries?
(A) Query 1 (B) Query 2 (C) Query 3 (D) Query 4
Q.13 Match the following:
Field Length in bits
P. UDP Header’s Port Number I. 48
Q. Ethernet MAC Address II. 8
R. IPv6 Next Header III. 32
S. TCP Header’s Sequence Number IV. 16
(A) P-III, Q-IV, R-II, S-I (B) P-II, Q-I, R-IV, S-III
(C) P-IV, Q-I, R-II, S-III (D) P-IV, Q-I, R-III, S-II
CS 4/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.14 Consider the following statements regarding the slow start phase of the TCP congestion
control algorithm. Note that cwnd stands for the TCP congestion window and MSS denotes
the Maximum Segment Size.
(i) The cwnd increases by 2 MSS on every successful acknowledgment.
(ii) The cwnd approximately doubles on every successful acknowledgement.
(iii) The cwnd increases by 1 MSS every round trip time.
(iv) The cwnd approximately doubles every round trip time.
Which one of the following is correct?
(A) Only (ii) and (iii) are true (B) Only (i) and (iii) are true
(C) Only (iv) is true (D) Only (i) and (iv) are true
Q.15 Two people, P and Q, decide to independently roll two identical dice, each with 6 faces,
numbered 1 to 6. The person with the lower number wins. In case of a tie, they roll the dice
repeatedly until there is no tie. Define a trial as a throw of the dice by P and Q. Assume that
all 6 numbers on each dice are equi-probable and that all trials are independent. The
probability (rounded to 3 decimal places) that one of them wins on the third trial is _____.
Q.16 π/4
The value of ∫0 x cos(x 2 )dx correct to three decimal places
(assuming that π = 3.14 ) is _____.
Q.17
Consider a matrix A uv
T where u 1 , v 1 . Note that vT denotes the
2 1
transpose of v. The largest eigenvalue of A is _____.
Q.18 The chromatic number of the following graph is _______.
CS 5/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.19 Let G be a finite group on 84 elements. The size of a largest possible proper subgroup of G
is ________.
Q.20 The postorder traversal of a binary tree is 8,9,6,7,4,5,2,3,1. The inorder traversal of the same
tree is 8,6,9,4,7,2,5,1,3. The height of a tree is the length of the longest path from the root to
any leaf. The height of the binary tree above is ______.
Q.21 Consider the following C program:
#include <stdio.h>
int counter = 0;
int calc (int a, int b) {
int c;
counter++;
if (b==3) return (a*a*a);
else {
c = calc(a, b/3);
return (c*c*c);
}
}
int main (){
calc(4, 81);
printf ("%d", counter);
}
The output of this program is _____.
Q.22 Consider the sequential circuit shown in the figure, where both flip-flops used are positive
edge-triggered D flip-flops.
in out
D Q D Q
clock
The number of states in the state transition diagram of this circuit that have a transition back
to the same state on some value of “in” is _____.
CS 6/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.23 A 32-bit wide main memory unit with a capacity of 1 GB is built using 256M × 4-bit DRAM
chips. The number of rows of memory cells in the DRAM chip is 214 . The time taken to
perform one refresh operation is 50 nanoseconds. The refresh period is 2 milliseconds. The
percentage (rounded to the closest integer) of the time available for performing the memory
read/write operations in the main memory unit is __________.
Q.24 Consider a system with 3 processes that share 4 instances of the same resource type. Each
process can request a maximum of K instances. Resource instances can be requested and
released only one at a time. The largest value of K that will always avoid deadlock is ____.
Q.25 Consider a long-lived TCP session with an end-to-end bandwidth of 1 Gbps (= 109 bits-per-
second). The session starts with a sequence number of 1234. The minimum time (in seconds,
rounded to the closest integer) before this sequence number can be used again is _______.
Q. 26 – Q. 55 carry two marks each.
Q.26 1
Consider a matrix P whose only eigenvectors are the multiples of .
4
Consider the following statements.
(I) P does not have an inverse
(II) P has a repeated eigenvalue
(III) P cannot be diagonalized
Which one of the following options is correct?
(A) Only I and III are necessarily true (B) Only II is necessarily true
(C) Only I and II are necessarily true (D) Only II and III are necessarily true
CS 7/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.27 Let N be the set of natural numbers. Consider the following sets.
P: Set of Rational numbers (positive and negative)
Q: Set of functions from {0, 1} to N
R: Set of functions from N to {0, 1}
S: Set of finite subsets of N.
Which of the sets above are countable?
(A) Q and S only (B) P and S only (C) P and R only (D) P, Q and S only
Q.28 Consider the first-order logic sentence
φ ≡ ∃s∃t∃u∀v∀w∀x∀y ψ(s, t, u, v, w, x, y)
where ψ(s, t, u, v, w, x, y) is a quantifier-free first-order logic formula using only predicate
symbols, and possibly equality, but no function symbols. Suppose φ has a model with a
universe containing 7 elements.
Which one of the following statements is necessarily true?
(A) There exists at least one model of φ with universe of size less than or equal to 3.
(B) There exists no model of φ with universe of size less than or equal to 3.
(C) There exists no model of φ with universe of size greater than 7.
(D) Every model of φ has a universe of size equal to 7.
CS 8/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.29 Consider the following C program:
#include<stdio.h>
void fun1(char *s1, char *s2){
char *tmp;
tmp = s1;
s1 = s2;
s2 = tmp;
}
void fun2(char **s1, char **s2){
char *tmp;
tmp = *s1;
*s1 = *s2;
*s2 = tmp;
}
int main(){
char *str1 = "Hi", *str2 = "Bye";
fun1(str1, str2); printf("%s %s ", str1, str2);
fun2(&str1, &str2); printf("%s %s", str1, str2);
return 0;
}
The output of the program above is
(A) Hi Bye Bye Hi (B) Hi Bye Hi Bye
(C) Bye Hi Hi Bye (D) Bye Hi Bye Hi
Q.30 Let G be a simple undirected graph. Let TD be a depth first search tree of G. Let TB be a
breadth first search tree of G. Consider the following statements.
(I) No edge of G is a cross edge with respect to TD. (A cross edge in G is between two
nodes neither of which is an ancestor of the other in TD.)
(II) For every edge (u,v) of G, if u is at depth i and v is at depth j in TB, then |i − j| = 1.
Which of the statements above must necessarily be true?
(A) I only (B) II only
(C) Both I and II (D) Neither I nor II
CS 9/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.31 Assume that multiplying a matrix G1 of dimension p × q with another matrix G2 of
dimension q × r requires pqr scalar multiplications. Computing the product of n matrices
G1G2G3…Gn can be done by parenthesizing in different ways. Define Gi Gi+1 as an explicitly
computed pair for a given paranthesization if they are directly multiplied. For example, in
the matrix multiplication chain G1G2G3G4G5G6 using parenthesization
(G1(G2G3))(G4(G5G6)), G2G3 and G5G6 are the only explicitly computed pairs.
Consider a matrix multiplication chain F1F2F3F4F5, where matrices F1, F2, F3, F4 and F5 are
of dimensions 2×25, 25×3, 3×16, 16×1 and 1×1000, respectively. In the parenthesization of
F1F2F3F4F5 that minimizes the total number of scalar multiplications, the explicitly
computed pairs is/are
(A) F1F2 and F3F4 only (B) F2F3 only
(C) F3F4 only (D) F1F2 and F4F5 only
Q.32 Consider the following C code. Assume that unsigned long int type length is 64
bits.
unsigned long int fun(unsigned long int n){
unsigned long int i, j = 0, sum = 0;
for (i = n; i > 1; i = i/2) j++;
for ( ; j > 1; j = j/2) sum++;
return(sum);
}
The value returned when we call fun with the input 240 is
(A) 4 (B) 5 (C) 6 (D) 40
Q.33 Consider the unsigned 8-bit fixed point binary number representation below,
b7 b6 b5 b4 b3 . b2 b1 b0
where the position of the binary point is between b3 and b2. Assume b7 is the most significant
bit. Some of the decimal numbers listed below cannot be represented exactly in the above
representation:
(i) 31.500 (ii) 0.875 (iii) 12.100 (iv) 3.001
Which one of the following statements is true?
(A) None of (i), (ii), (iii), (iv) can be exactly represented
(B) Only (ii) cannot be exactly represented
(C) Only (iii) and (iv) cannot be exactly represented
(D) Only (i) and (ii) cannot be exactly represented
CS 10/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.34 The size of the physical address space of a processor is 2P bytes. The word length is
2W bytes. The capacity of cache memory is 2N bytes. The size of each cache block is
2M words. For a K-way set-associative cache memory, the length (in number of bits) of the
tag field is
(A) P − N − log 2 K (B) P − N + log 2 K
(C) P − N − M − W − log 2 K (D) P − N − M − W + log 2 K
Q.35 Consider the following languages:
I. {am b n c p d q | m + p = n + q, where m, n, p, q ≥ 0}
II. {am b n c p d q | m = n and p = q, where m, n, p, q ≥ 0}
III. {am b n c p d q | m = n = p and p ≠ q, where m, n, p, q ≥ 0}
IV. {am b n c p d q | mn = p + q, where m, n, p, q ≥ 0}
Which of the languages above are context-free?
(A) I and IV only (B) I and II only
(C) II and III only (D) II and IV only
Q.36 Consider the following problems. L(G) denotes the language generated by a grammar G.
L(M) denotes the language accepted by a machine M.
(I) For an unrestricted grammar G and a string w, whether w ∈ L(G)
(II) Given a Turing machine M, whether L(M) is regular
(III) Given two grammars G1 and G2 , whether L(G1 ) = L(G2 )
(IV) Given an NFA N, whether there is a deterministic PDA P such that N and P
accept the same language.
Which one of the following statements is correct?
(A) Only I and II are undecidable (B) Only III is undecidable
(C) Only II and IV are undecidable (D) Only I, II and III are undecidable
CS 11/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.37 A lexical analyzer uses the following patterns to recognize three tokens T1, T2, and T3 over
the alphabet {a,b,c}.
T1 : a? (b|c)∗ a
T2 : b? (a|c)∗ b
T3 : c? (b|a)∗ c
Note that ‘x?’ means 0 or 1 occurrence of the symbol x. Note also that the analyzer outputs
the token that matches the longest possible prefix.
If the string bbaacabc is processed by the analyzer, which one of the following is the
sequence of tokens it outputs?
(A) T1 T2 T3 (B) T1 T1 T3 (C) T2 T1 T3 (D) T3 T3
Q.38 Consider the following parse tree for the expression a#b$c$d#e#f, involving two binary
operators $ and #.
Which one of the following is correct for the given parse tree?
(A) $ has higher precedence and is left associative; # is right associative
(B) # has higher precedence and is left associative; $ is right associative
(C) $ has higher precedence and is left associative; # is left associative
(D) # has higher precedence and is right associative; $ is left associative
CS 12/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.39 In
0 a system, there are three types of resources: E, F and G. Four processes P0, P1, P2 and P3
execute concurrently. At the outset, the processes have declared their maximum resource
requirements using a matrix named Max as given below. For example, Max[P2,F] is the
maximum number of instances of F that P2 would require. The number of instances of the
resources allocated to the various processes at any given state is given by a matrix named
Allocation.
Consider a state of the system with the Allocation matrix as shown below, and in which 3
instances of E and 3 instances of F are the only resources available.
Allocation Max
E F G E F G
P0 1 0 1 P0 4 3 1
P1 1 1 2 P1 2 1 4
P2 1 0 3 P2 1 3 3
P3 2 0 0 P3 5 4 1
From the perspective of deadlock avoidance, which one of the following is true?
(A) The system is in safe state.
(B) The system is not in safe state, but would be safe if one more instance of E were
available
(C) The system is not in safe state, but would be safe if one more instance of F were
available
(D) The system is not in safe state, but would be safe if one more instance of G were
available
CS 13/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.40 Consider the following solution to the producer-consumer synchronization problem. The
shared buffer size is N. Three semaphores empty, full and mutex are defined with respective
initial values of 0, N and 1. Semaphore empty denotes the number of available slots in the
buffer, for the consumer to read from. Semaphore full denotes the number of available slots
in the buffer, for the producer to write to. The placeholder variables, denoted by P, Q, R,
and S, in the code below can be assigned either empty or full. The valid semaphore
operations are: wait() and signal().
Producer: Consumer:
do{ do{
wait(P); wait(R);
wait(mutex); wait(mutex);
//Add item to buffer //Consume item from buffer
signal(mutex); signal(mutex);
signal(Q); signal(S);
}while(1); }while(1);
Which one of the following assignments to P, Q, R and S will yield the correct solution?
(A) P: full, Q: full, R: empty, S: empty
(B) P: empty, Q: empty, R: full, S: full
(C) P: full, Q: empty, R: empty, S: full
(D) P: empty, Q: full, R: full, S: empty
Q.41 Consider the relations r(A, B) and s(B, C), where s.B is a primary key and r.B is a foreign
key referencing s.B. Consider the query
Q: r ⋈ (σB<5 (s))
Let LOJ denote the natural left outer-join operation. Assume that r and s contain no null
values.
Which one of the following queries is NOT equivalent to Q?
(A) σB<5 (r ⋈ s) (B) σB<5 (r LOJ s)
(C) r LOJ (σB<5 (s)) (D) σB<5 (r) LOJ s
CS 14/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.42 Consider the following four relational schemas. For each schema, all non-trivial functional
dependencies are listed. The underlined attributes are the respective primary keys.
Schema I: Registration (rollno, courses)
Field ‘courses’ is a set-valued attribute containing the set of courses a student has
registered for.
Non-trivial functional dependency:
rollno courses
Schema II: Registration (rollno, courseid, email)
Non-trivial functional dependencies:
rollno, courseid email
email rollno
Schema III: Registration (rollno, courseid, marks, grade)
Non-trivial functional dependencies:
rollno, courseid marks, grade
marks grade
Schema IV: Registration (rollno, courseid, credit)
Non-trivial functional dependencies:
rollno, courseid credit
courseid credit
Which one of the relational schemas above is in 3NF but not in BCNF?
(A) Schema I (B) Schema II (C) Schema III (D) Schema IV
Q.43 Let G be a graph with 100! vertices, with each vertex labelled by a distinct permutation of
the numbers 1,2, … , 100. There is an edge between vertices u and v if and only if the label
of u can be obtained by swapping two adjacent numbers in the label of v. Let y denote the
degree of a vertex in G, and z denote the number of connected components in G.
Then, y + 10z = _____.
CS 15/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.44 Consider Guwahati (G) and Delhi (D) whose temperatures can be classified as high (H),
medium (M) and low (L). Let P(HG ) denote the probability that Guwahati has high
temperature. Similarly, P(MG ) and P(LG ) denotes the probability of Guwahati having
medium and low temperatures respectively. Similarly, we use P(HD ), P(MD ) and P(LD ) for
Delhi.
The following table gives the conditional probabilities for Delhi’s temperature given
Guwahati’s temperature.
HD MD LD
HG 0.40 0.48 0.12
MG 0.10 0.65 0.25
LG 0.01 0.50 0.49
Consider the first row in the table above. The first entry denotes that if Guwahati has high
temperature (HG ) then the probability of Delhi also having a high temperature (HD ) is 0.40;
i.e., P(HD |HG ) = 0.40. Similarly, the next two entries are P(MD |HG ) = 0.48 and
P(LD |HG ) = 0.12. Similarly for the other rows.
If it is known that P(HG ) = 0.2, P(MG ) = 0.5, and P(LG ) = 0.3, then the probability
(correct to two decimal places) that Guwahati has high temperature given that Delhi has high
temperature is _______.
Q.45 Consider the following program written in pseudo-code. Assume that x and y are integers.
Count(x,y) {
if (y != 1){
if (x != 1) {
print("*");
Count(x/2, y);
}
else {
y = y-1;
Count(1024, y);
}
}
}
The number of times that the print statement is executed by the call
Count(1024,1024) is _____.
Q.46 The number of possible min-heaps containing each value from {1, 2, 3, 4, 5, 6, 7} exactly once
is _____.
CS 16/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.47 Consider the following undirected graph G:
4 x
1 3
4
5
4
Choose a value for x that will maximize the number of minimum weight spanning trees
(MWSTs) of G. The number of MWSTs of G for this value of x is ______.
Q.48 Consider the weights and values of items listed below. Note that there is only one unit of
each item.
Item number Weight Value
(in Kgs) (in Rupees)
1 10 60
2 7 28
3 4 20
4 2 24
The task is to pick a subset of these items such that their total weight is no more than 11 Kgs
and their total value is maximized. Moreover, no item may be split. The total value of items
picked by an optimal algorithm is denoted by Vopt . A greedy algorithm sorts the items by
their value-to-weight ratios in descending order and packs them greedily, starting from the
first item in the ordered list. The total value of items picked by the greedy algorithm is
denoted by Vgreedy .
The value of Vopt − Vgreedy is ____________.
Q.49 Consider the minterm list form of a Boolean function F given below.
F(P, Q, R, S) = ∑ m(0, 2, 5, 7, 9, 11) + d(3, 8, 10, 12, 14)
Here, m denotes a minterm and d denotes a don’t care term. The number of essential prime
implicants of the function F is ______.
CS 17/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.50 The instruction pipeline of a RISC processor has the following stages: Instruction Fetch (IF),
Instruction Decode (ID), Operand Fetch (OF), Perform Operation (PO) and Writeback (WB).
The IF, ID, OF and WB stages take 1 clock cycle each for every instruction. Consider a
sequence of 100 instructions. In the PO stage, 40 instructions take 3 clock cycles each, 35
instructions take 2 clock cycles each, and the remaining 25 instructions take 1 clock cycle
each. Assume that there are no data hazards and no control hazards.
The number of clock cycles required for completion of execution of the sequence of
instructions is ______.
Q.51 A processor has 16 integer registers (R0, R1, .. , R15) and 64 floating point registers (F0,
F1,… , F63). It uses a 2-byte instruction format. There are four categories of instructions:
Type-1, Type-2, Type-3, and Type-4. Type-1 category consists of four instructions, each
with 3 integer register operands (3Rs). Type-2 category consists of eight instructions, each
with 2 floating point register operands (2Fs). Type-3 category consists of fourteen
instructions, each with one integer register operand and one floating point register operand
(1R+1F). Type-4 category consists of N instructions, each with a floating point register
operand (1F).
The maximum value of N is __________.
Q.52 Given a language L, define Li as follows:
L0 = {ε}
Li = Li−1 ⋅ L for all i > 0
The order of a language L is defined as the smallest k such that Lk = Lk+1 .
Consider the language L1 (over alphabet 0) accepted by the following automaton.
0
0
0
The order of L1 is _____.
CS 18/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.53 Consider a storage disk with 4 platters (numbered as 0, 1, 2 and 3), 200 cylinders (numbered
as 0, 1, … , 199), and 256 sectors per track (numbered as 0, 1, … , 255). The following 6
disk requests of the form [sector number, cylinder number, platter number] are received by
the disk controller at the same time:
[120, 72, 2] , [180, 134, 1] , [60, 20, 0] , [212, 86, 3] , [56, 116, 2] , [118, 16, 1]
Currently the head is positioned at sector number 100 of cylinder 80, and is moving towards
higher cylinder numbers. The average power dissipation in moving the head over 100
cylinders is 20 milliwatts and for reversing the direction of the head movement once is 15
milliwatts. Power dissipation associated with rotational latency and switching of head
between different platters is negligible.
The total power consumption in milliwatts to satisfy all of the above disk requests using the
Shortest Seek Time First disk scheduling algorithm is _______.
Q.54 Consider an IP packet with a length of 4,500 bytes that includes a 20-byte IPv4 header and
a 40-byte TCP header. The packet is forwarded to an IPv4 router that supports a Maximum
Transmission Unit (MTU) of 600 bytes. Assume that the length of the IP header in all the
outgoing fragments of this packet is 20 bytes. Assume that the fragmentation offset value
stored in the first fragment is 0.
The fragmentation offset value stored in the third fragment is _______.
CS 19/20
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GATE 2018 COMPUTER SCIENCE AND INFORMATION TECHNOLOGY
Q.55 Consider a simple communication system where multiple nodes are connected by a shared
broadcast medium (like Ethernet or wireless). The nodes in the system use the following
carrier-sense based medium access protocol. A node that receives a packet to transmit will
carrier-sense the medium for 5 units of time. If the node does not detect any other
transmission in this duration, it starts transmitting its packet in the next time unit. If the node
detects another transmission, it waits until this other transmission finishes, and then begins
to carrier-sense for 5 time units again. Once they start to transmit, nodes do not perform any
collision detection and continue transmission even if a collision occurs. All transmissions
last for 20 units of time. Assume that the transmission signal travels at the speed of 10 meters
per unit time in the medium.
Assume that the system has two nodes P and Q, located at a distance d meters from each
other. P starts transmitting a packet at time t=0 after successfully completing its carrier-sense
phase. Node Q has a packet to transmit at time t=0 and begins to carrier-sense the medium.
The maximum distance d (in meters, rounded to the closest integer) that allows Q to
successfully avoid a collision between its proposed transmission and P’s ongoing
transmission is _____.
END OF THE QUESTION PAPER
CS 20/20
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Q.No. Type Section Key/Range Marks 1 MCQ GA B 1 2 MCQ GA A 1 3 MCQ GA D 1 4 MCQ GA C 1 5 MCQ GA B 1 6 MCQ GA B 2 7 MCQ GA C 2 8 MCQ GA B 2 9 MCQ GA A 2 10 MCQ GA C 2 1 MCQ CS D 1 2 MCQ CS A 1 3 MCQ CS B 1 4 MCQ CS D 1 5 MCQ CS D 1 6 MCQ CS D 1 7 MCQ CS B 1 8 MCQ CS B 1 9 MCQ CS A 1 10 MCQ CS B 1 11 MCQ CS A 1 12 MCQ CS D 1 13 MCQ CS C 1 14 MCQ CS C 1
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Q.No. Type Section Key/Range Marks 15 NAT CS 0.021 to 0.024 1 16 NAT CS 0.27 to 0.30 1 17 NAT CS 3 to 3 1 18 NAT CS 3 to 3 1 19 NAT CS 42 to 42 1 20 NAT CS 4 to 4 1 21 NAT CS 4 to 4 1 22 NAT CS 2 to 2 1 23 NAT CS 59.0 to 60.0 1 24 NAT CS 2 to 2 1 25 NAT CS 34 to 35 1 26 MCQ CS D 2 27 MCQ CS D 2 28 MCQ CS A 2 29 MCQ CS A 2 30 MCQ CS A 2 31 MCQ CS C 2 32 MCQ CS B 2 33 MCQ CS C 2 34 MCQ CS B 2 35 MCQ CS B 2 36 MCQ CS D 2 37 MCQ CS D 2 38 MCQ CS A 2
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Q.No. Type Section Key/Range Marks 39 MCQ CS A 2 40 MCQ CS C 2 41 MCQ CS C 2 42 MCQ CS B 2 43 NAT CS 109 to 109 2 44 NAT CS 0.60 to 0.62 2 45 NAT CS 10230 to 10230 2 46 NAT CS 80 to 80 2 47 NAT CS 4 to 4 2 48 NAT CS 16 to 16 2 49 NAT CS 3 to 3 2 50 NAT CS 219 to 219 2 51 NAT CS 32 to 32 2 52 NAT CS 2 to 2 2 53 NAT CS 85 to 85 2 54 NAT CS 144 to 144 2 55 NAT CS 50 to 50 2
Official key not published for this paper.
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Source: GATE. Question paper published by GATE.