In a positive logic system powered near 5 V, which voltage level commonly represents a HIGH (logic 1) state?

Introduction:
Positive logic assigns higher voltages to logic 1 (HIGH) and lower voltages to logic 0 (LOW). In many introductory contexts, examples reference 5 V systems.

Given Data / Assumptions:

• Positive logic convention.
• Nominal supply around 5 V, a common educational reference.
• We seek a typical HIGH level under this convention.

Concept / Approach:
In positive logic, logic 1 corresponds to a higher potential. With a 5 V supply, the canonical HIGH level is near +5 V, while 0 V corresponds to LOW. Real devices accept a range (e.g., ≥ 2.0 V for TTL), but +5 V is the archetypal level.

Step-by-Step Solution:

Verification / Alternative check:
Thresholds vary by family (TTL/CMOS), but illustrative teaching uses +5 V for HIGH and 0 V for LOW in positive logic with 5 V rails.

Why Other Options Are Wrong:

• 0 V: LOW in positive logic.
• +1 V: Below typical VIH(min); not reliably HIGH.
• +9 V: Exceeds the assumed 5 V system; not representative and may damage inputs.

Common Pitfalls:
Confusing positive logic mapping with exact VIH thresholds; the concept is mapping, not the precise datasheet limits.

Final Answer:
+5 V