UGC NET Computer Science 2020 Previous Year Questions (PYQs) – Page 1 of 10
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The period of a signal is $100\ ms$. Then the frequency of this signal in kilohertz is ______
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Solution
Period $T=100\ ms=0.1\ sec$
Frequency:
$f=\frac{1}{T}=\frac{1}{0.1}=10\ Hz$
Now convert into kHz:
$10\ Hz=\frac{10}{1000}\ kHz=0.01\ kHz=10^{-2}\ kHz$
Frequency:
$f=\frac{1}{T}=\frac{1}{0.1}=10\ Hz$
Now convert into kHz:
$10\ Hz=\frac{10}{1000}\ kHz=0.01\ kHz=10^{-2}\ kHz$
The process of removing details from a given state representation is called ______
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Solution
Abstraction means hiding or removing unnecessary details and keeping only important information.
So, removing details from a state representation is called abstraction.
So, removing details from a state representation is called abstraction.
Which of the following is NOT true in problem solving in artificial intelligence?
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Solution
AI problem solving commonly uses heuristic search.
In AI, solution steps may not always be explicit, and knowledge may be imprecise.
Repetition mechanism is mainly a feature of conventional algorithmic programming, not a special feature of AI problem solving.
In AI, solution steps may not always be explicit, and knowledge may be imprecise.
Repetition mechanism is mainly a feature of conventional algorithmic programming, not a special feature of AI problem solving.
If $f(x)=$ $x$ is my friend, and $p(x)=$ $x$ is perfect, then the correct logical translation of the statement “some of my friends are not perfect” is:
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Solution
“Some” means there exists at least one person.
“my friends” means $f(x)$.
“not perfect” means $\neg p(x)$.
So, the statement becomes:
$\exists x(f(x)\land \neg p(x))$
“my friends” means $f(x)$.
“not perfect” means $\neg p(x)$.
So, the statement becomes:
$\exists x(f(x)\land \neg p(x))$
What kind of clauses are available in conjunctive normal form?
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Solution
In CNF, formula is written as conjunction of clauses.
Each clause is a disjunction of literals.
Example:
$(p\vee \neg q)\wedge(r\vee s)$
Here, $(p\vee \neg q)$ and $(r\vee s)$ are clauses.
So, clauses in CNF are disjunction of literals.
Each clause is a disjunction of literals.
Example:
$(p\vee \neg q)\wedge(r\vee s)$
Here, $(p\vee \neg q)$ and $(r\vee s)$ are clauses.
So, clauses in CNF are disjunction of literals.
Consider the following properties:
A. Reflexive
B. Antisymmetric
C. Symmetric
Let $A=\{a,b,c,d,e,f,g\}$ and
$R=\{(a,a),(b,b),(c,d),(c,g),(d,g),(e,e),(f,f),(g,g)\}$
be a relation on $A$. Which of the following property/properties is/are satisfied by the relation $R$?
A. Reflexive
B. Antisymmetric
C. Symmetric
Let $A=\{a,b,c,d,e,f,g\}$ and
$R=\{(a,a),(b,b),(c,d),(c,g),(d,g),(e,e),(f,f),(g,g)\}$
be a relation on $A$. Which of the following property/properties is/are satisfied by the relation $R$?
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Solution
For reflexive relation, every element must have pair $(x,x)$.
But $(c,c)$ and $(d,d)$ are missing.
So, relation is not reflexive.
For antisymmetric relation, if $(x,y)$ and $(y,x)$ both exist, then $x=y$.
Here, no reverse pair exists for $(c,d),(c,g),(d,g)$.
So, relation is antisymmetric.
For symmetric relation, if $(x,y)$ exists, then $(y,x)$ must also exist.
But $(c,d)$ exists and $(d,c)$ does not exist.
So, relation is not symmetric.
Therefore, relation satisfies B and not A.
But $(c,c)$ and $(d,d)$ are missing.
So, relation is not reflexive.
For antisymmetric relation, if $(x,y)$ and $(y,x)$ both exist, then $x=y$.
Here, no reverse pair exists for $(c,d),(c,g),(d,g)$.
So, relation is antisymmetric.
For symmetric relation, if $(x,y)$ exists, then $(y,x)$ must also exist.
But $(c,d)$ exists and $(d,c)$ does not exist.
So, relation is not symmetric.
Therefore, relation satisfies B and not A.
Consider the following argument with premise $\forall x(P(x)\vee Q(x))$ and conclusion $(\forall xP(x))\wedge(\forall xQ(x))$
| (A) $\forall x(P(x)\vee Q(x))$ | Premise |
| (B) $P(c)\vee Q(c)$ | Universal instantiation from (A) |
| (C) $P(c)$ | Simplification from (B) |
| (D) $\forall xP(x)$ | Universal generalization of (C) |
| (E) $Q(c)$ | Simplification from (B) |
| (F) $\forall xQ(x)$ | Universal generalization of (E) |
| (G) $(\forall xP(x))\wedge(\forall xQ(x))$ | Conjunction of (D) and (F) |
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Solution
From $\forall x(P(x)\vee Q(x))$, we can get:
$P(c)\vee Q(c)$
So, step (B) is correct.
But from $P(c)\vee Q(c)$, we cannot conclude $P(c)$ alone.
Also, we cannot conclude $Q(c)$ alone.
So, steps (C) and (E) are not correct inferences.
Step (G) would be correct only if (D) and (F) were validly obtained.
Hence, the main error is in steps (C) and (E).
$P(c)\vee Q(c)$
So, step (B) is correct.
But from $P(c)\vee Q(c)$, we cannot conclude $P(c)$ alone.
Also, we cannot conclude $Q(c)$ alone.
So, steps (C) and (E) are not correct inferences.
Step (G) would be correct only if (D) and (F) were validly obtained.
Hence, the main error is in steps (C) and (E).
Which of the following are applications of symbol table?
A. Storage allocation
B. Checking type compatibility
C. Suppressing duplicate error messages
Choose the correct answer from the options given below:
A. Storage allocation
B. Checking type compatibility
C. Suppressing duplicate error messages
Choose the correct answer from the options given below:
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Solution
Symbol table stores information about identifiers like name, type, scope, address and other attributes.
It helps in storage allocation.
It helps in checking type compatibility.
It also helps in avoiding or suppressing duplicate error messages for the same identifier.
So, all A, B and C are correct.
It helps in storage allocation.
It helps in checking type compatibility.
It also helps in avoiding or suppressing duplicate error messages for the same identifier.
So, all A, B and C are correct.
Simplified expression/s for following Boolean function
$F(A,B,C,D)=\sum(0,1,2,3,6,12,13,14,15)$
is/are
(A) $A'B' + AB + A'C'D'$
(B) $A'B' + AB + A'CD'$
(C) $A'B' + AB + BC'D'$
(D) $A'B' + AB + BCD'$
Choose the correct answer from the options given below:
$F(A,B,C,D)=\sum(0,1,2,3,6,12,13,14,15)$
is/are
(A) $A'B' + AB + A'C'D'$
(B) $A'B' + AB + A'CD'$
(C) $A'B' + AB + BC'D'$
(D) $A'B' + AB + BCD'$
Choose the correct answer from the options given below:
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Solution
Given minterms are:
$0,1,2,3,6,12,13,14,15$
$A'B'$ covers minterms $0,1,2,3$
$AB$ covers minterms $12,13,14,15$
Remaining minterm is $6$
Option (B):
$A'CD'$ covers minterms $2,6$
Both are present in the function.
So, option (B) is correct.
Option (D):
$BCD'$ covers minterms $6,14$
Both are present in the function.
So, option (D) is also correct.
Options (A) and (C) include minterm $4$, which is not present in the function.
$0,1,2,3,6,12,13,14,15$
$A'B'$ covers minterms $0,1,2,3$
$AB$ covers minterms $12,13,14,15$
Remaining minterm is $6$
Option (B):
$A'CD'$ covers minterms $2,6$
Both are present in the function.
So, option (B) is correct.
Option (D):
$BCD'$ covers minterms $6,14$
Both are present in the function.
So, option (D) is also correct.
Options (A) and (C) include minterm $4$, which is not present in the function.
Which of the following statements with respect to K-segment pipelining are true?
(A) Maximum speedup that a pipeline can provide is k theoretically.
(B) It is impossible to achieve maximum speedup k in k-segment pipeline.
(C) All segments in pipeline take same time in computation.
Choose the correct answer from the options given below:
(A) Maximum speedup that a pipeline can provide is k theoretically.
(B) It is impossible to achieve maximum speedup k in k-segment pipeline.
(C) All segments in pipeline take same time in computation.
Choose the correct answer from the options given below:
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Solution
In a k-segment pipeline, theoretical maximum speedup is $k$.
So, statement A is true.
In practical cases, due to pipeline filling time, emptying time, delays and unequal stages, exact maximum speedup $k$ is not achieved.
So, statement B is true.
All pipeline segments need not take exactly the same computation time.
So, statement C is false.
So, statement A is true.
In practical cases, due to pipeline filling time, emptying time, delays and unequal stages, exact maximum speedup $k$ is not achieved.
So, statement B is true.
All pipeline segments need not take exactly the same computation time.
So, statement C is false.
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