
In
Summary
Thus, the three key
features of "modern" computers are that they are:
 digital
Modern computers are digital, because they mimic the operations of arithmetic
by manipulating devices that represent the digits of
numbers.
 binary
Modern computers are binary, because the kind of arithmetic they mimic
is not that of our favored decimal (base10) numbers but, rather, arithmetic
operations upon binary (base2) numbers.
 electronic
Modern computers mechanize arithmetic. In other words, they
are machines that do arithmetic, in the sense that they are built to
mimic the rules of arithmetic: that is, given some input representing
an arithmetic instruction, the machine is built so that, blindly and
automatically, its switches flip to the states representing the appropriate
result.

