A computer is a programmablemachine (or more precisely, a programmablesequential state machine).There are two basic kinds of computers: analog and digital.
Analog computers are analog devices.That is, they have continuous states rather than discrete numbered states. Ananalog computer can represent fractional or irrational values exactly, with noround-off. Analog computers are almost never used outside of experimentalsettings.
A digital computer is aprogrammable clocked sequential state machine. A digital computer uses discretestates. A binary digital computer uses two discrete states, such aspositive/negative, high/low, on/off, used to represent the binary digits zeroand one.
The French word ordinateur,meaning that which puts things in order, is a good description of the mostcommon functionality of computers.