LogFAQs > #894845036

Computers are definitely up there. No one person intimately understands how it all works. People designing hardware or software only really understand the small part they're in charge of.

Nobody knows everything about anything. But some people know a lot.

Electricity is a fundamental force of nature that acts on electric charges, pulling them together or pushing them apart. This force, when normalized for arbitrary charge and then applied over a distance is called voltage. Because of the chemical properties of various metals and semiconductors (number of valence electrons, for example), atoms of those elements placed closely together, as in solids, can be passed easily from one to another as long as a replacement is provided. For that reason, attaching a conductor between two different potentials (a voltage difference) causes the conductor's valence electrons to eqperience electric force that encourages them to flow. The electrons move from the lower potential to the higher, which is logically equivalent to a positive charge moving from higher to lower (this is why people are confused about which direction current flows).

Power consumed is in terms of energy per time. Voltge is energy per charge and current is charge per time, meaning that power is current times voltage. If there is no voltage or no current, power is zero.

Because it's all about fields, you can put a small break in the circuit, and if you out a plate on each end, the field resulting from the difference in potential will attract electrons to one terminal and "holes" (lack of electron) to the other. This is called a capacitor.

There are two kinds of silicon, N and P, which are "doped" appropriately (by filling them with electrons or "holes" (a hole is a lack of an electron) that encourage or discourage the movement of electrons. These are used to build all kinds of semiconductor devices, but the most relevant to computing is the Field-Effect Transistor, or FET. A FET places a piece of silicon between the two terminals of a capacitor. Then a voltge placed across the capacitor causes the electrons and holes to separate within the silicon, creating a narrrow band where conductivity is high and electrons can flow freely.

Combining these FETs in series and in parallel allows data encoded in high and low voltages to be aggregated with gates, or logical constructs like "if this and that, do this" or "if neither this nor that, do this." This is called combinational logic. Using two types of FETs to route to the higher voltage and to the lower voltage is a technology called CMOS that allows the output range to match the input range and cuts power consumption drastically. Since all potential voltage differences are zero where there is a closed circuit (except when switching) and all currents are zero where there is a difference in potential, steady-state power is zero.

Combinational logic can do all kinds of stuff, including addition of binary numbers and ither mathematics.

But because the movement of electrons in an FET is limited by the strength of the field, and barring that, the universal speed limit, each FET takes a short amount of time to switch, which consumes power because currents flows briefly while the conductivity of the silicon band increases.

But another effect of the switching time is that it allows what is called sequential logic, where data can be stored in a construct called a flip-flop, in an arrangement so that it reinforces itself, and more relevantly, can be passed from one to another sequentially and simultaneously. The first flip-flop can be given an input value while the next reads its output value.

Sequential logic circuits can be used to shift/transfer data and perform complex calculations.
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