# Logic Design Questions and Answers – Registers and Register Transfers

This set of Logic Design Multiple Choice Questions & Answers (MCQs) focuses on “Registers and Register Transfers”.

1. A D Flip-Flop can store 2 bits of information. True or False?
a) True
b) False

Explanation: A D Flip-Flop can store only 1 bit of information, since the inputs and outputs are 1 bit wide. At an instance it can store either 0 or 1. A D Flip-Flop cannot store more than 1 bit of information.

2. If ‘n’ number of D Flip-Flops are grouped together with a common clock to form a register, then that register can store ‘n’ bits of information.
a) True
b) False

Explanation: A D Flip-Flop can store only 1 bit of information, since the inputs and outputs are 1 bit wide. So, if a register has ‘n’ D Flip-Flops with a common clock, then it can store ‘n’ bits of information.

3. In Digital Electronics, what is a bus?
a) A wire
b) A pin of an integrated circuit
c) A kind of Random Access Memory
d) A group of wires that perform a common function

Explanation: A group of wires that perform a common function is referred to as a bus. Example for a bus is the USB (Universal Serial Bus). Busses are used when many bits of data need to be transferred between devices.

4. Identify the electronic device associated with the following symbol.

a) Tri-state buffer with active low control
b) Tri-state buffer with active high control
c) 3:1 Multiplexer
d) NOT gate

Explanation: The above symbol is that of a tri-state buffer with Active Low control. The bubble on the control input indicates that it is Active low.
Truth table:

Control Output
0 Input
1 Z (High Impedance)

5. Identify the electronic device associated with the following symbol.

a) Tri-state buffer with active low control
b) Tri-state buffer with active high control
c) 3:1 Multiplexer
d) NOT gate

Explanation: The above symbol is that of a tri-state buffer with Active High control.
Truth table:

Control Output
0 Z (High Impedance)
1 Input

6. Identify the electronic device associated with the following symbol.

a) Buffer
b) NOT gate
c) OR gate
d) NOR gate

Explanation: The above symbol is that of a buffer. The output of a buffer is 0 when the input is 0 and 1 when the input is 1. A buffer can also be obtained by cascading 2 NOT gates.

Sanfoundry Global Education & Learning Series – Logic Design.