Binary numbers might seem terribly inefficient since they seem to be a lot longer than decimal numbers. In fact, the binary equivalent of a decimal number will never be more than 3 times as long, when counting the actual digits. But computers do not see 1 and 0 the same as 4 or 5 or 7. The decimal digits would have be represented somehow using electricity, and though there are ways to do this, such as using ten different voltage levels, none are as simple or reliable as using off and on; hence the binary system.