Counter modulus (MOD) definition: Evaluate the statement: “The modulus of a counter is the actual number of unique states in its counting sequence,” for example MOD-10 for a decade counter.

Introduction / Context:
Modulus (often noted MOD or modulo) is a fundamental characteristic of counters. It tells you how many distinct states the counter cycles through before returning to its starting state. Recognizing modulus helps you design timing chains, frequency dividers, and numerical displays.

Given Data / Assumptions:

• A counter produces a sequence of states (usually binary or coded).
• After a fixed number of states, the sequence repeats.
• The modulus equals the count of unique states per cycle.

Concept / Approach:
For a straight binary N-bit counter, the modulus is 2^N. For decade (BCD) counters, the modulus is 10 because the sequence resets after 10 states (0000 through 1001). Custom modulo counters use decoding to reset at a chosen terminal count, defining their modulus accordingly.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets and textbooks label counters as MOD-N to indicate division ratio and sequence length, matching observed behavior in timing diagrams.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing modulus with maximum binary value; forgetting that illegal or skipped states in custom counters still define the modulus by the actual repeating sequence length.

Final Answer:
Correct