In order to understand how a computer is able to manipulate data and perform computations, you must first understand how data is represented by a computer.
At the lowest level, the indivisible unit of data in a computer is a bit . A bit represents a single binary value, which may be either 1 or 0. In different contexts, a bit value of 1 and 0 may also be referred to as ``true'' and ``false'', ``yes'' and ``no'', ``high'' and ``low'', ``set'' and ``not set'', or ``on'' and ``off''.
The decision to use binary values, rather than something larger (such as decimal values) was not purely arbitrary- it is due in a large part to the relative simplicity of building electronic devices that can manipulate binary values.