Computers
Last updated: May 11, 2007.
It was probably the worst prediction in
history. Back in the 1940s,
Thomas Watson, boss of the giant IBM Corporation, reputedly forecast
that the world would need no more than “about five computers”. Six
decades later and the global population of computers has now risen to
something like one billion machines!
To be fair to Watson, computers
have changed enormously in that time. In the 1940s, they were giant
scientific and military behemoths commissioned by the government at a
cost of millions of dollars apiece; today, most computers are not even
recognisable as such: they are embedded in everything from microwave ovens to cellphones and digital
radios. What makes computers flexible enough to work in all these
different appliances? How come they are so phenomenally useful? And how
exactly do they work?
Photo: A typical laptop computer.
What is a computer?
A computer is an electronic machine that processes information—in other
words, an information processor: it takes in
raw information
(or data) at one end, stores it until it’s
ready to work on it, chews
and crunches it for a bit, then spits out the results at the other end.
All these processes have a name. Taking in information is called input,
storing information is better known as memory,
chewing
information is also known as processing, and
spitting out
results is called output.
Photo caption: Computers that used to take up a huge room now fit comfortably on your finger!
Public domain photo courtesy of the U.S. Department of Energy.
Imagine if a computer were a person. Suppose you have a friend who’s
really good at math. She
is so good that everyone she knows posts their math problems to
her. Each morning, she goes to her letterbox and finds a pile of
new math problems waiting for her attention. She piles them up on her
desk until she
gets around to looking at them. Each afternoon, she takes a letter off
the top of the pile, studies the problem, works out the
solution, and scribbles the answer on the back. She puts
this in an envelope addressed to the person who sent her the original
problem and sticks it in her out tray, ready to post. Then she moves to
the next letter in the pile. You can see that your friend is working
just like a computer. Her letterbox is her input; the pile on her desk
is her memory; her brain is the processor that works out the solutions
to the problems; and the out tray on her desk is her output.
Once you understand that computers are about input, storage,
processing, and output, all the junk on your desk makes a lot more
sense. Your keyboard and mouse, for
example, are just input units—ways of getting information into your
computer that it can process. If you use a microphone and voice recognition software, that's
another form of input. Your computer probably stores all your documents
and files on a hard-drive: a huge
magnetic memory. But smaller, computer-based devices like digital
cameras and cellphones use other kinds of storage such as flash memory cards. As for output, your
computer almost certainly has a screen and probably also stereo loudspeakers. You may have an inkjet printer on your desk too to make
a more permanent form of output. Your computer's processor (sometimes
known as the central processing unit) is a
microchip buried deep inside. It works amazingly hard and gets
incredibly hot in the process. That's why your computer has a little
fan blowing away—to stop its brain from overheating!
Artwork caption: A computer works by combining input, storage, processing, and output.
All the main parts of a computer system are involved in one of these four processes.
Thinking by numbers
As you can read in our long article on computer history, the first
computers were gigantic calculating machines and all they ever really
did was “crunch numbers”: solve lengthy, difficult, or tedious
mathematical problems. Today, computers work on a much wider variety of
problems—but they are all still, essentially, calculations. Everything
a computer does, from helping you to edit a photograph you’ve taken
with a digital camera to displaying
a web page, involves manipulating numbers in one way or another.
Suppose you’re looking at a digital photo you just taken in a paint or
photo-editing program and you decide you want a mirror image of it (in
other words, flip it
from left to right). You probably know that the photo is made up of
millions of individual pixels (coloured squares) arranged in a grid
pattern. The computer stores each pixel as a number, so taking a
digital
photo is really like an instant, orderly exercise in painting by
numbers! To flip a digital photo, the computer simply reverses the
sequence of numbers so they run from right to left instead of left to
right. Or suppose you want to make the photograph brighter. All you
have
to do is slide the little “brightness” icon. The computer then works
through all the pixels, increasing the brightness value for each one
by, say, 10 percent to make the entire image brighter. So, once again,
the problem boils down to numbers and calculations.
What makes a computer different from a calculator is that it can work
all by itself. You just give it your instructions (called a program)
and off it goes, performing a long and complex series of operations all
by itself. Back in the 1970s and 1980s, if you wanted a home computer
to do almost anything at all, you had to write your own little program
to do it. For example, before you could write a letter on a computer,
you had to write a program that would read the letters you typed on the
keyboard, store them in the memory, and display them on the screen.
Writing the program usually took more time than doing whatever it
was that you had originally wanted to do (writing the letter). Pretty
soon, people started selling programs like word processors to save you
the need to write programs yourself.
Today, most computer users buy, download, or share programs like
Microsoft Word and Excel. Hardly anyone writes programs any more. Most
people see their computers as tools that help them do jobs, rather than
complex electronic machines they have to pre-program—and that’s just as
well, because most of us have better things to do than computer
programming.
The beauty of a computer is that it can run a word-processing one
minute—and then a photo-editing program five seconds later. In other
words, although we
don’t really think of it this way, the computer can be reprogrammed as
many times as you like.This is why programs are also called software.
They’re “soft” in the sense that they are not fixed: they can be
changed easily. By contrast, a computer’s hardware—the
bits and
pieces from which it is made (and the peripherals,
like the
mouse and printer, you plug into it)—is pretty much fixed when you buy
it off the shelf. The hardware is what makes your computer powerful;
the ability to run different software is what makes it flexible. That
computers can do so many different jobs is what makes them so useful—and that's why millions of us can no longer live
without them!
Photo caption: Computers can crack tricky mathematical problems much faster than humans. This colourful model of the structure of a protein was drawn by a powerful supercomputer at Argonne National Laboratory. Public domain photo courtesy of the U.S. Department of Energy.
Go shop
.
