A one is not a one. It is a voltage. At the bottom of every computation sits a slab of silicon and a decision about electricity. Binary exists because transistors are excellent at two things and terrible at everything in between: fully on, fully off. Ask a transistor to hold a precise intermediate value and thermal noise, manufacturing variation and supply ripple will corrupt it within microseconds. Ask it to sit at 0 V or 0.8 V and it will hold that state against considerable abuse. The workhorse is the MOSFET. Three terminals plus the body: - Gate, insulated from everything by a few nanometres of oxide - Source and drain, two doped regions in the substrate - The channel between them, which conducts only when the gate says so Put a positive voltage on the gate of an NMOS device and the field pulls electrons toward the surface, inverting the region beneath the oxide into a conducting channel. Below the threshold voltage, no channel, no current. Above it, current flows. That thresho...