Binary adders in digital electronics A standard binary adder (parallel adder built from full-adder stages) is designed to add how many binary numbers simultaneously?

Introduction / Context:
Binary adders are foundational arithmetic circuits used in ALUs, microcontrollers, and digital signal processors. A parallel binary adder is typically constructed from cascaded full-adder stages to add two multi-bit binary numbers at the same time. This question checks whether you understand how many operands a conventional binary adder handles concurrently.

Given Data / Assumptions:

• A “binary adder” refers to the common ripple-carry or look-ahead adder composed of full-adders.
• Each full-adder stage accepts bits from two operands and a carry-in.
• We are not discussing multi-operand compressor trees unless otherwise stated.

Concept / Approach:
A full-adder takes three 1-bit inputs: A, B, and Cin. The A and B inputs are the two operand bits, while Cin is a carry propagated from the previous (lower significant) stage. Although three inputs exist, only two of them are operand bits; the third is a carry chain signal, not an independent third number. Therefore, a standard parallel adder adds exactly two multi-bit binary numbers at once.

Step-by-Step Solution:
Recognize full-adder inputs: A, B are operand bits; Cin is carry.Cascading n full-adders forms an n-bit adder for two n-bit operands.Hence, the binary adder adds 2 numbers simultaneously.

Verification / Alternative check:
Block diagrams of ripple-carry and carry look-ahead adders universally show two operand buses (X and Y) and a single carry-in line, confirming the two-operand design.

Why Other Options Are Wrong:

• 4, 6, 8: These imply multi-operand addition in a single stage, which would require compressor trees (e.g., carry-save adders) or sequential accumulation, not a standard binary adder.

Common Pitfalls:

• Confusing carry-in with a third independent operand.
• Assuming accumulation over time (adding many numbers sequentially) equates to simultaneous multi-operand addition.

Final Answer:
2