Practice Digital Logic MCQs with answers. Logic gates, Boolean algebra, flip-flops, combinational circuits — fully solved for GATE 2026. These MCQs are perfect for NTS, PPSC, FPSC, CSS, OTS, UPSC, GATE, UGC NET, bank exams, university exams, and job interviews. The bold green option ✅ is the correct answer.
Number Systems
1. Binary number system has base:
a) 8 b) 10 c) 16 d) 2 ✅
2. Hexadecimal uses digits:
a) 0-7 b) 0-9 c) 0-9 and A-F (base 16) ✅ d) 0-1
3. Binary equivalent of decimal 15 is:
a) 1100 b) 1010 c) 1111 ✅ d) 10000
4. 1 byte can represent values 0 to:
a) 127 b) 100 c) 255 ✅ d) 511
⚡ Logic Gates
5. AND gate gives output 1 when:
a) Any input is 1 b) ALL inputs are 1 ✅ c) No input is 1 d) Only one input is 1
6. OR gate gives output 1 when:
a) All inputs are 0 b) At least one input is 1 ✅ c) All inputs are 1 d) No inputs
7. NOT gate:
a) Adds two bits b) Inverts the input ✅ c) Multiplies inputs d) Stores data
8. NAND gate is:
a) AND + OR b) NOT + AND (inverted AND) ✅ c) OR + NOT d) XOR + AND
Boolean Algebra
9. In Boolean algebra, A + 0 =:
a) 0 b) 1 c) A ✅ d) A complement
10. In Boolean algebra, A * 1 =:
a) 0 b) 1 c) A ✅ d) A complement
11. De Morgans theorem: (A+B) complement =:
a) A+B b) A complement . B c) A complement . B complement ✅ d) A.B
Sequential Circuits
12. A flip-flop stores:
a) 8 bits b) 1 bit of data ✅ c) 1 byte d) 1 KB
13. A register is:
a) A single flip-flop b) A group of flip-flops for storing multiple bits ✅ c) A logic gate d) An ALU
14. A counter is used to:
a) Store data permanently b) Count the number of pulses/events ✅ c) Convert analog to digital d) Amplify signals
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