BCD (Binary-Coded Decimal) decoders — number of output lines In digital electronics, a standard BCD-to-decimal decoder accepts a 4-bit BCD input (0000 to 1001 for digits 0–9). How many distinct output lines does such a BCD decoder provide to represent decimal digits?

Introduction / Context:
A BCD (Binary-Coded Decimal) to decimal decoder converts a 4-bit BCD input into a one-of-ten output pattern where exactly one line is active for the digit being represented. This question checks basic decoder literacy used in counters, seven-segment drivers, and numeric multiplexed displays.

Given Data / Assumptions:

• Input code is BCD: valid codes 0000 through 1001 represent 0–9.
• Invalid BCD inputs 1010–1111 are typically suppressed or treated as don’t-care.
• Output style is one-of-N (one line active at a time).

Concept / Approach:
A BCD-to-decimal decoder must generate a unique output for each decimal digit 0–9. Therefore there must be 10 outputs. Internally, combinational logic decodes the 4-bit input and drives the corresponding output line active, while all others remain inactive.

Step-by-Step Solution:

Verification / Alternative check:
Common ICs (e.g., 7442/7445 families) are 4-to-10 decoders/decoders-drivers, confirming the 10-line requirement.

Why Other Options Are Wrong:

• 4: This is the number of BCD input bits, not outputs.
• 8: Would suit octal decoding, not decimal BCD.
• 16: Corresponds to full 4-to-16 binary decoding, not restricted to BCD 0–9.

Common Pitfalls:
Confusing a 4-to-16 binary decoder with a BCD-to-decimal decoder; BCD decoders restrict outputs to 10 valid digits.

Final Answer:
10