What are Computers?
Computers are
machines that perform tasks or calculations according to a set of instructions,
or programs. The first fully electronic computers, introduced in the 1940s,
were huge machines that required teams of people to operate. Compared to those
early machines, today's computers are amazing. Not only are they thousands of
times faster, they can fit on your desk, on your lap, or even in your pocket.
Computers work through an interaction of hardware and software. Hardware refers
to the parts of a computer that you can see and touch, including the case and
everything inside it. The most important piece of hardware is a tiny
rectangular chip inside your computer called the Central Processing Unit (CPU),
or microprocessor. It's the "brain" of your computer—the part that
translates instructions and performs calculations. Hardware items such as your
monitor, keyboard, mouse, printer, and other components are often called
hardware devices, or devices.
Software refers
to the instructions, or programs, that tell the hardware what to do. A
word-processing program that you can use to write letters on your computer is a
type of software. The operating system (OS) is software that manages the
computer and the devices connected to it. Windows is a well-known operating
system.
What can do with computers?
In the workplace, many people use computers to keep records, analyze
data, do research, and manage projects. At home, you can use computers to find
information, store pictures and music, track finances, play games, and
communicate with others—and those are just a few of the possibilities. You can
also use your computer to connect to the Internet, a network that links
computers around the world. Internet access is available for a monthly fee in most
urban areas, and increasingly, in less populated areas. With Internet access,
you can communicate with people all over the world and find a vast amount of
information. Here are some of the most popular things to do with computers: the
web, E-mail, Instant messaging, Pictures, music, movies, and gaming.3
Types of Computers
Computers range in size and capability. At one end of the scale are
supercomputers, very large computers with thousands of linked microprocessors
that perform extremely complex calculations. At the other end are tiny
computers embedded in cars, TVs, stereo systems, calculators, and appliances.
These computers are built to perform a limited number of tasks. The personal
computer, or PC, is designed to be used by one person at a time. This section
describes the various kinds of personal computers: desktops, laptops,
handheld computers, and Tablet PCs.
• Desktop computers
Desktop computers are designed for use at a desk or table. They are
typically larger and more powerful than other types of personal computers.
Desktop computers are made up of separate components. The main component,
called the system unit, is usually a rectangular case that sits on or
underneath a desk. Other components, such as the monitor, mouse, and keyboard,
connect to the system unit.
• Laptop computers and small notebook PCs
Laptop computers are lightweight mobile PCs with a thin screen. Laptops
can operate on batteries, so you can take them anywhere. Unlike desktops,
laptops combine the CPU, screen, and keyboard in a single case. The screen
folds down onto the keyboard when not in use. Small notebook PCs (often
referred to as mini-notebooks), are small, affordable laptops that are designed
to perform a limited number of tasks. They're usually less powerful than a
laptop, so they're used mainly to browse the web and check e-mail.4
• Smart phones
Smart phones are mobile phones that have some of the same capabilities as
a computer. You can use a smart phone to make telephone calls, access the
Internet, organize contact information, send e-mail and text messages, play
games, and take pictures. Smart phones usually have a keyboard and a large
screen.
• Handheld computers
Handheld computers, also called personal digital assistants (PDAs), are
battery-powered computers small enough to carry almost anywhere. Although not
as powerful as desktops or laptops, handheld computers are useful for
scheduling appointments, storing addresses and phone numbers, and playing
games. Some have more advanced capabilities, such as making telephone calls or
accessing the Internet. Instead of keyboards, handheld computers have touch
screens that you use with your finger or a stylus (a pen-shaped pointing tool).
• Tablet PCs
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Tablet PCs are mobile PCs that combine features of laptops
and handheld computers. Like laptops, they're powerful and have a built-in
screen. Like handheld computers, they allow you to write notes or draw
pictures on the screen, usually with a tablet pen (the pen that come with
table and is used to interact with items in the screen) instead of a stylus.
They can also convert your handwriting into typed text. Some Tablet PCs are
“convertibles” with a screen that swivels and unfolds to reveal a keyboard
underneath.5 ENIAC
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Introduced in 1946, ENIAC (Electronic Numerical Integrator
and Computer) was the first general-purpose electronic computer. It was built
for the United States military to calculate the paths of artillery shells.
Physically, ENIAC was enormous, weighing more than 27,000 kilograms (60,000
pounds) and filling a large room. To process data, ENIAC used about 18,000
vacuum tubes, each the size of a small light bulb. The tubes burned out
easily and had to be constantly replaced.
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