Any operation labeled "Serial" typically requires a clock and memory, making it sequential. "Parallel" versions of the same operation are usually combinational.
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.
