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We are all familiar with what a computer is in a specific, contemporary sense. Personal computers (PCs) are found in most aspects of daily life, and for some it is hard to even imagine a world without them. But the term means more than simply the Macs and PCs we are familiar with. A computer is, at its most basic, a machine which can take instructions, and perform computations based on those instructions.

It is the ability to take instructions — often known as programs — and execute them, that distinguishes a computer from a mechanical calculator. While both are able to make computations, a calculator responds simply to immediate input. In fact, most modern calculators are actually computers, with a number of pre-installed programs to help aid in complex tasks.

Computers range from the very small to the very large. Some are capable of doing millions of calculations in a single second, while others may take long periods of time to do even the most simple calculations. But theoretically, anything one computer is capable of doing, another will also be able to do. Given the right instructions, and sufficient memory, a computer found in a wristwatch should be able to accomplish anything a supercomputer can — although it might take thousands of years for the wristwatch to complete the operation.

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