The purpose of C is to precisely define a series of operations that a computer can perform to accomplish a task. Most of these operations involve manipulating numbers and text, but anything that the computer can physically do can be programmed in C.
Computers have no intelligence- they have to be told exactly what to do and this is defined by the programming language you use. Once programmed they can repeat the steps as many times as you wish at very high speed. Modern PCs are so fast they can count to a billion in a second or two.
