Digital Logic

Step 1: Understanding the Concept:
- Combinational Circuits: Output depends only on current inputs. No memory elements.
- Sequential Circuits: Output depends on current inputs and previous states. Uses memory (flip-flops).
Step 2: Detailed Explanation:
- P) Serial Adder: Adds bits bit-by-bit over time. It requires a flip-flop to store the carry for the next bit addition. Thus, it is a Sequential Circuit (2).
- Q) Parallel Adder: Adds all bits of a word simultaneously using logic gates. No memory is needed. Thus, it is a Combinational Circuit (1).
- R) BCD to 7 Segment Decoder: Converts a 4-bit BCD input to 7 output signals to drive a display. It is a Combinational Circuit (1).
- S) Priority Encoder: Encodes inputs based on priority using purely logic gates. It is a Combinational Circuit (1).
Step 3: Final Answer:
The correct match is P-2, Q-1, R-1, S-1.

Step 1: Understanding the Concept:
A serial-in serial-out (SISO) shift register loads bits one by one. To "completely load" means filling all flip-flops. To "unload" means shifting all stored bits out through the output terminal.
Step 2: Detailed Explanation:
1. To load bits into an -bit register, it takes clock pulses. For a 4-bit register, loading takes 4 pulses.
2. After the 4th pulse, the first bit is already at the output.
3. To shift out the remaining bits, we need more pulses.
4. Total pulses = .
Step 3: Final Answer:
The total clock pulses required is 7.