ISRO CSE 2020 PYQ ⋆ CSE Study247

Question 76

MCQ · Single Correct 1 mark

Previous Year Question ISRO CSE 2020 PYQ

If $A={x$, y, z} and $B={u$, v, w, x}, and the universe is {s, t, u, v, w, x, y, z}. Then (A U B') n (A n B) is equal to

A {u,v,w,x} B {x} C {u,v,w,x,y,z} D {u,v,w}

Question 77

MCQ · Single Correct 1 mark

Previous Year Question ISRO CSE 2020 PYQ

Consider the logic circuit network comparing A, B, C, D, E, F signals. Which Boolean function is implemented?

A (AB)' E + EF + (CD)' F B (A'B' + E)(E' +F')(C+ D + F') C (E' + AB F')(C + D + F') D (A + B) E' + EF' + CD F'

📘 Solution & Detailed Explanation

🔢 Step-by-Step Solution

Step-by-Step Derivation:

Find the outputs of the first level of gates:

CODE

• Top NAND gate: \(\overline{AB}\)
	• Bottom NOR gate: \(\overline{C+D}\)

Find the outputs of the three AND gates:

CODE

• Top AND gate: \(\overline{AB} \cdot E\)
	• Middle AND gate: \(E \cdot F\)
	• Bottom AND gate: \(\overline{C+D} \cdot F\)

CODE

Find the expression for the final NOR gate:
\(\text{Output}=\overline{(\overline{AB}\cdot E)+(E\cdot F)+(\overline{C+D}\cdot F)}\)

CODE

Simplify using De Morgan's Law (\(\overline{X + Y + Z} = \bar{X} \cdot \bar{Y} \cdot \bar{Z}\)):
	• \(\bar{X} = \overline{\overline{AB} \cdot E} = \overline{\overline{AB}} + \bar{E} = AB + \bar{E}\)
	• \(\bar{Y} = \overline{E \cdot F} = \bar{E} + \bar{F}\)
	• \(\bar{Z} = \overline{\overline{C+D} \cdot F} = (C + D) + \bar{F}\)
Multiplying them together gives:
\(\text{Output}=(\={E}+AB)(\={E}+\={F})(C+D+\={F})\)

CODE

Combine the first two terms using Boolean algebra rules:
\((\={E}+AB)(\={E}+\={F})=\={E}\={E}+\={E}\={F}+AB\={E}+AB\={F}\)
Since \(\bar{E} + \bar{E}\bar{F} + \bar{E}AB = \bar{E}\) (by absorption law), this reduces to:
\(\={E}+AB\={F}\)

CODE

Substitute back to get the final form:
\(\text{Output}=(\={E}+AB\={F})(C+D+\={F})\)

Question 78

MCQ · Single Correct 1 mark

Previous Year Question ISRO CSE 2020 PYQ

In the following procedure:

CODE

Integer procedure P(X,Y);
Integer X,Y;
value x;
begin
      K=5;
      L=8;
      P=x+y;
end
X is called by value and Y is called by name. If the procedure were invoked by the following program fragment:
K=0;
L=0;
Z=P(K,L);
then the value of Z will be set equal to

A 5 B 8 C 13 D 0

Question 79

MCQ · Single Correct 1 mark

Previous Year Question ISRO CSE 2020 PYQ

Consider product of three matrices M1, M2 and M3 having w rows and x columns, x rows and y columns, and y rows and z columns. Under what condition will it take less time to compute the product as (M1 M2) M3 than to compute M1 (M2 M3) ?

A Always take the same time B (1 / x + 1 / z) < (1 / w + 1 / y) C x > y D (w + x) > (y + z)

Question 80

MCQ · Single Correct 1 mark

Previous Year Question ISRO CSE 2020 PYQ

A new flipflop with inputs X and Y, has the following property:

CODE

X=0, Y=0 -> Next State = 1
X=0, Y=1 -> Next State = Q'
X=1, Y=1 -> Next State = 0
X=1, Y=0 -> Next State = Q
Which of the following expresses the next state in terms of X, Y, current state Q?

A (X' ^ Q') v (Y' ^ Q) B (X' ^ Q) v (Y' ^ Q') C (X ^ Q') v (Y ^ Q) D (X ^ Q') v (Y' ^ Q)

📘 Solution & Detailed Explanation

🔢 Step-by-Step Solution

Detailed Explanation:

CODE

Evaluating truth table for Q_next(X, Y, Q):
   (0,0,0)->1, (0,0,1)->1, (0,1,0)->1, (0,1,1)->0, (1,0,0)->0, (1,0,1)->1, (1,1,0)->0, (1,1,1)->0.

Simplifying gives Q_next = (X' AND Q') OR (Y' AND Q).