The fact that electronic computers are now used for data processing has led the general
public to believe that it is a mysterious, complicated science and that the computers are
giant brains. Both of these ideas are false. A computer is basically just a high-speed adding
machine that performs the functions it is told to. If the input data are varied even a little,
the computer is unable to operate until it is programmed to accept the variations. The
business operations it performs are impressive only because of the extremely high speed of manipulation, but most of these operations have been used for decades. Unlike man, the
computer performs repetitive calculations without getting tired or bored.

What is the central idea?