In digital logic, a binary adder circuit is designed to add how many binary numbers at a time in a single operation?

Introduction / Context:
Binary adders are fundamental arithmetic blocks used in ALUs, counters, and DSP datapaths. Understanding the basic operand count clarifies how wider operations (e.g., accumulation) are architected from simpler units.

Given Data / Assumptions:

• A “binary adder” refers to a standard two-operand adder cell (half/full adder or n-bit adder).
• Carry-in may supply an additional 1-bit term but does not constitute a third full-width operand.
• Outputs include the sum and a carry-out.

Concept / Approach:
Conventional adders combine two n-bit inputs, A and B. The carry-in Cin represents a single-bit extension (e.g., for chaining adders or forming increment operations), not a third n-bit operand. Multi-operand addition uses trees (carry-save adders or compressors) that reduce several inputs to two before a final 2-operand addition.

Step-by-Step Solution:

Verification / Alternative check:
Schematic symbols and HDL entities for adders universally expose two data inputs (A, B) plus optional Cin, matching the two-operand model.

Why Other Options Are Wrong:

• 1: An adder needs at least two operands.
• 3 or 5: Multi-operand sums require reduction stages; a single adder does not directly add three or more n-bit numbers in one step.

Common Pitfalls:
Misinterpreting Cin as a third operand; confusing compressor trees with final adders.

Final Answer:
2