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1

By combining logic gates complex systems such as processors and memory can be built using:

Medium 2 Marks

What mathematical tool describes how logic gates are combined?

A Machine code programs

B Boolean expressions

C Assembly language instructions

D Decimal arithmetic

2

How many combinations in the truth table of an AND gate with 2 inputs produce output 1?

Medium 2 Marks

AND gate is very restrictive — only one row gives output 1.

A 1

B 2

C 3

D 4

3

A security system grants access only when BOTH a password and fingerprint are verified. Which gate models this?

Medium 2 Marks

Which gate requires ALL conditions to be satisfied?

A OR gate

B NOT gate

C AND gate

D NAND gate

4

How many rows in the truth table of a 2-input OR gate produce output 0?

Medium 2 Marks

OR gives 0 only when every input is 0 — how many ways can that happen with 2 inputs?

A 0

B 1

C 2

D 3

5

A light turns ON when darkness is detected (sensor = 0). Which gate models this behaviour?

Medium 2 Marks

Which gate flips 0 to 1 and 1 to 0?

A AND gate

B OR gate

C NOT gate

D NOR gate

6

What are universal gates?

Medium 2 Marks

These special gates can replace every other gate.

A Gates that only work with decimal numbers

B Gates that can implement any Boolean function and recreate all other logic gates

C Gates used only in memory circuits

D The three fundamental gates AND OR NOT

7

Why are NAND and NOR gates called universal gates?

Medium 2 Marks

What makes a gate universal in digital circuit design?

A Because they are the most commonly used gates in computers

B Because any digital circuit can be built using only NAND gates or only NOR gates

C Because they process both binary and decimal data

D Because they have the highest output voltage

8

What is the Boolean expression for a NAND gate?

Medium 2 Marks

Start with AND then apply NOT to the result.

A A + B

B (A + B) prime

C (A · B) prime

D A prime + B prime

9

For a NAND gate with A=1 and B=1 what is the output?

Medium 2 Marks

NAND is the inverse of AND — when AND gives 1 NAND gives 0.

A 1

B 0

C Undefined

D 2

10

For a NAND gate with A=0 and B=1 what is the output?

Medium 2 Marks

NAND gives 0 only when every input is 1 — otherwise output is 1.

A 0

B 1

C Undefined

D Depends on voltage

11

What is the Boolean expression for a NOR gate?

Medium 2 Marks

Start with OR then apply NOT to the result.

A (A · B) prime

B A + B

C (A + B) prime

D A prime · B prime

12

For a NOR gate with A=1 and B=0 what is the output?

Medium 2 Marks

Apply OR first then invert — if OR gives 1 then NOR gives 0.

A 1

B 0

C Undefined

D Depends on voltage

13

For a NOR gate with A=1 and B=1 what is the output?

Medium 2 Marks

Apply OR then invert — OR of 1 and 1 is 1 which inverts to 0.

A 1

B 0

C Undefined

D Both 0 and 1

14

How many rows does a truth table have for a circuit with 3 inputs?

Medium 2 Marks

Use the formula 2 to the power of n where n is the number of inputs.

A 4 rows

B 6 rows

C 8 rows

D 16 rows

15

What are Boolean expressions?

Medium 2 Marks

Think about how algebra represents arithmetic — Boolean expressions represent logic.

A Programs written in binary language

B Mathematical representations of logical operations using Boolean variables and operators

C Formulas used in spreadsheet calculations

D Methods to convert decimal to binary

16

In a combinational circuit the output depends on:

Medium 2 Marks

No memory means only present inputs matter — no past states.

A Previous outputs stored in memory

B Only the current inputs with no memory element

C Both current inputs and previous stored outputs

D The speed of the processor

17

Which of the following is an example of a combinational circuit?

Medium 2 Marks

Which option performs a calculation based only on current input values?

A Counter

B Shift register

C Adder

D Flip-flop

18

In a sequential circuit the output depends on:

Medium 2 Marks

Sequential circuits remember past states — they have memory.

A Only the current inputs

B The speed of the clock signal

C Both current inputs AND previous outputs (memory)

D The type of logic gates used

19

Which of the following is an example of a sequential circuit?

Medium 2 Marks

Which option needs to remember its previous state to function?

A Adder

B Decoder

C Multiplexer

D Counter

20

Which gate produces output 0 only when all inputs are 1?

Medium 2 Marks

AND gives 1 when all inputs are 1 — NAND gives the opposite.

A AND gate

B OR gate

C NOT gate

D NAND gate

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