Ring & Johnson Counters — These are widely used shift-register-based counters (sequence generators), not “uncommon” circuits. Evaluate the statement.

Introduction:
Ring counters and Johnson (twisted-ring) counters are classic sequence generators built from shift registers. They appear in timing generators, state machines with simple decoding, LED chasers, and clock-division applications. The claim that they are “uncommon” is inaccurate in both education and industry contexts.

Given Data / Assumptions:

• Ring counter: a single 1 circulates through a ring of flip-flops.
• Johnson counter: the inverted output of the last stage is fed back to the first, producing 2N distinct states with N flip-flops.
• Synchronous clocking is typical; decoding is straightforward.

Concept / Approach:
Because these counters provide easily decodable one-hot or two-hot patterns with low logic overhead, they are favored where simple, glitch-resistant state outputs are needed. Their usage is common in CPLD/FPGA designs and discrete TTL/CMOS projects alike.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

Common Pitfalls:

Final Answer: