FREE LESSON · Physics & signals · 1 OF 6
What Is a Bit in Computer Science?
A bit is a physical agreement: Stable distinctions in a noisy world
Zero and one are regions, not perfect voltages.
A physical device exposes a continuous quantity such as voltage, charge, light, or magnetization. Engineers assign ranges of that quantity to symbols. A receiver uses thresholds to decide which symbol arrived; noise margins compare guaranteed sender output levels with accepted receiver input thresholds. The gap between receiver thresholds is an unspecified input region, not itself a noise margin.
Digital reliability comes from restoring a symbol at boundaries, not from eliminating analog physics.
Regeneration breaks the accumulation of small errors
Suppose 0–0.8 V means low and 2–3.3 V means high. A gate receiving 2.7 V does not forward “2.7” as an increasingly degraded fact; it produces a fresh high-level output. Cascaded gates therefore restore logical levels, within their timing and electrical limits.
Regeneration is why billions of imperfect analog devices can implement long digital computations.
Sources and further reading
- Signals and Systems: MIT OpenCourseWare
- Introduction to EECS I: MIT OpenCourseWare · open text and labs