Multi-digit decimal addition using BCD adders: When several-digit decimal numbers are added using BCD, ________.

Introduction / Context:
Binary-coded decimal (BCD) represents each decimal digit with a 4-bit nibble. Adding multi-digit decimal values requires per-digit correction (adding 0110 when a nibble exceeds 1001 or generates a carry) and proper carry propagation to higher digits.

Given Data / Assumptions:

• Each decimal digit = 4-bit BCD nibble.
• Nibble sums may need +0110 correction.
• Digit-to-digit carry must propagate.

Concept / Approach:
Build the adder as a cascade: one BCD adder stage per decimal digit (ones, tens, hundreds, …). Each stage performs binary add of the two BCD nibbles plus Cin, then conditionally adds 0110 if needed, outputting a corrected BCD nibble and a carry to the next stage.

Step-by-Step Solution:

Verification / Alternative check:
Worked examples of multi-digit BCD sums show each digit independently corrected with carries chained upward.

Why Other Options Are Wrong:

Common Pitfalls:
Forgetting that a nibble 1010–1111 is invalid BCD and must be corrected.

Final Answer:
a separated BCD adder is required for each digit position