Practice 50 chapter-wise MCQs covering digital logic, analog and digital signals, logic gates, Boolean functions and expressions, Boolean identities, duality, switches, truth tables and logic diagrams.
1. A digital system primarily represents information using:
A) Discrete values such as binary 0 and 1 B) Only decimal fractions C) Only continuous voltages D) Only mechanical motion
2. A digital signal differs from an analog signal because a digital signal:
A) Must always be sinusoidal B) Uses discrete levels rather than a continuously varying range C) Cannot carry information D) Can only be transmitted through wires
3. In binary digital logic, the two basic logic states are commonly represented by:
A) 2 and 3 B) 5 and 10 C) 0 and 1 D) -1 and +1 only
4. A logic gate is a circuit that:
A) Stores an entire program B) Measures temperature C) Generates mechanical power D) Performs a logical operation on one or more inputs
5. The output of an AND gate is 1 when:
A) All of its inputs are 1 B) At least one input is 1 C) All of its inputs are 0 D) Exactly one input is 0
6. The output of an OR gate is 0 when:
A) At least one input is 1 B) All inputs are 0 C) Exactly one input is 1 D) The inputs are different
7. A NOT gate performs which operation?
A) Addition B) Multiplication C) Inversion D) Division
8. If the input to a NOT gate is 1, its output is:
A) 1 B) 2 C) Undefined D) 0
9. For an AND gate with inputs A and B, the Boolean expression for the output Y is:
A) Y = A · B B) Y = A + B C) Y = A' D) Y = A ⊕ B
10. For an OR gate with inputs A and B, the Boolean expression for the output Y is:
A) Y = A · B B) Y = A + B C) Y = A' D) Y = B'
11. In Boolean algebra, the symbol commonly used for logical NOT of A is:
A) A + 1 B) A · 0 C) A' D) A + A
12. The Boolean expression A + 0 simplifies to:
A) 0 B) A' C) 1 D) A
13. The Boolean expression A · 1 simplifies to:
A) A B) 1 C) 0 D) A'
14. The Boolean expression A + 1 is equal to:
A) A B) 1 C) 0 D) A'
15. The Boolean expression A · 0 is equal to:
A) A B) 1 C) A' D) 0
16. The identity A + A = A is known as the:
A) Complement law B) Commutative law C) Distributive law D) Idempotent law
17. The expression A + A' evaluates to:
A) 1 B) 0 C) A D) A'
18. The expression A · A' evaluates to:
A) 1 B) A C) 0 D) A'
19. The commutative law for OR states that:
A) A + 0 = A B) A · 1 = A C) A + B = B + A D) A + A = A
20. The commutative law for AND states that:
A) A + B = A − B B) A + B = B + A C) A · 0 = A D) A · B = B · A
21. The dual of the Boolean identity A + 0 = A is:
A) A · 1 = A B) A + 1 = A C) A · 0 = A D) A' + 0 = A
22. Which gate is equivalent to an AND gate followed by a NOT gate?
A) NOR B) NAND C) XOR D) OR
23. Which gate is equivalent to an OR gate followed by a NOT gate?
A) AND B) NAND C) NOR D) XOR
24. A NAND gate produces output 0 only when:
A) All inputs are 0 B) At least one input is 0 C) Exactly one input is 1 D) All inputs are 1
25. A NOR gate produces output 1 only when:
A) All inputs are 0 B) All inputs are 1 C) At least one input is 1 D) The inputs are different
26. An XOR gate with two inputs produces 1 when:
A) Both inputs are 1 B) The two inputs are different C) Both inputs are 0 D) Neither input exists
27. For two inputs A and B, A XOR B is 0 when:
A) A = 0 and B = 1 B) A = 1 and B = 0 C) A and B are equal D) A and B are always different
28. A truth table shows:
A) Only the gate symbol B) Only the input names C) Only the final output D) All possible input combinations and their corresponding outputs
29. A two-input logic gate has how many possible input combinations?
A) 4 B) 2 C) 8 D) 16
30. A three-input logic gate has how many possible input combinations?
A) 6 B) 8 C) 9 D) 12
31. For n binary inputs, the number of possible input combinations is:
A) n² B) 2n C) 2ⁿ D) n + 2
32. The truth table for a NOT gate has:
A) Four rows B) Eight rows C) Three rows D) Two rows
33. If A = 1 and B = 0, the output of A AND B is:
A) 0 B) 1 C) 2 D) Undefined
34. If A = 1 and B = 0, the output of A OR B is:
A) 0 B) 1 C) 2 D) Undefined
35. If A = 1 and B = 0, the output of A XOR B is:
A) 0 B) 2 C) 1 D) Undefined
36. If A = 0 and B = 0, the output of A NOR B is:
A) 0 B) 2 C) Undefined D) 1
37. If A = 1 and B = 1, the output of A NAND B is:
A) 0 B) 1 C) 2 D) Undefined
38. A switch in a simple digital circuit can be used to represent:
A) Only analog temperature B) A binary input state such as open/closed C) A complete truth table D) A Boolean identity by itself
39. In a basic switch representation, an open switch may be associated with:
A) Only decimal 10 B) A permanently high signal C) A binary 0 state D) A binary number with eight digits
40. A closed switch in a simple digital circuit may represent:
A) Only an error B) A floating input C) A decimal fraction D) A binary 1 state
41. A Boolean function relates:
A) One or more Boolean inputs to a Boolean output B) Only decimal numbers to physical units C) Only text to images D) Only analog signals to sound
42. Which expression represents the OR of A and B?
A) A · B B) A + B C) A' D) A ⊕ B
43. Which expression represents the AND of A and B?
A) A + B B) A' + B' C) A · B D) A ⊕ B
44. Which statement about NAND is correct?
A) It is an OR gate without inversion B) It always produces 1 C) It is identical to XOR D) It is the complement of AND
45. Which statement about NOR is correct?
A) It is the complement of OR B) It is the complement of AND C) It is identical to XOR D) It never produces 0
46. Which gate gives 1 when its two inputs are different?
A) AND B) XOR C) NOR D) NAND
47. Which Boolean operator is represented by logical multiplication?
A) OR B) NOT C) AND D) XOR
48. Which Boolean operator is represented by logical addition?
A) NOT B) AND C) XOR D) OR
49. A logic diagram is used to:
A) Graphically represent the logical operations in a digital circuit B) Show only physical dimensions C) Display only decimal calculations D) Replace all truth tables
50. If a Boolean expression has two inputs, its truth table should include:
These MCQs are prepared with reference to the FBISE HSSC-I Computer Science Assessment Framework and the National Curriculum of Pakistan 2022–23. Chapter 1 covers SLO CS-11-A-01 and its stated learning content, including Boolean functions, Boolean expressions, Boolean identities, duality, digital logic, analog and digital signals, logic gates, truth tables and switches. The framework also emphasizes constructing Boolean expressions and identities, recognizing duality, identifying logic gates, creating truth tables for up to three inputs, and representing Boolean expressions with logic gates.