Counters and decade operation: A BCD (decade) counter counts 0–9 and then resets. Which binary state range does it skip during counting?

Introduction / Context:
Decade (BCD) counters represent decimal digits (0 through 9) in binary-coded decimal. After reaching 1001 (decimal 9), they reset to 0000 and do not pass through states representing 10–15 in pure binary. Recognizing the skipped range is essential in counter design and state-diagram logic.

Given Data / Assumptions:

• Counter outputs are four-bit binary codes.
• Valid outputs: 0000 (0) to 1001 (9).
• Invalid / skipped outputs: binary 10 to 15.

Concept / Approach:
Binary states from 1010 to 1111 correspond to decimal 10 through 15. In BCD counting, these states are inhibited or quickly forced back to 0000 via synchronous or asynchronous reset logic.

Step-by-Step Solution:

Verification / Alternative check:
BCD truth tables and 74xx decade counter datasheets (e.g., 7490/7493 derived designs with gating) confirm reset at 10.

Why Other Options Are Wrong:

Common Pitfalls:

Final Answer: