Unit 2
If you use a desktop computer, you might already know that there isn't any
single part called the "computer". A computer is really a system of
many parts working together. The physical parts, which you can see and touch,
are collectively calledhardware.
(Software, on the other hand,
refers to the instructions, or programs, that tell the hardware what to do.)
The illustration below shows the most common hardware in a desktop computer
system. Your system may look a little different, but it probably has most of
these parts. A laptop computer has similar parts but combines them into a
single notebook-sized package.
Let's take a
look at each of these parts.
1. System unit
The system unit is the core of a
computer system. Usually it's a rectangular box placed on or underneath your
desk. Inside this box are many electronic components that process information.
The most important of these components is the central processing unit (CPU), or microprocessor, which acts as the "brain" of your
computer. Another component is random
access memory (RAM), which temporarily stores information that the CPU
uses while the computer is on. The information stored in RAM is erased when the
computer is turned off.
Almost every
other part of your computer connects to the system unit using cables. The
cables plug into specific ports(openings),
typically on the back of the system unit. Hardware that is not part of the
system unit is sometimes called a peripheral
device or device.
Storage
Your
computer has one or more disk
drives—devices that store information on a metal or plastic disk. The
disk preserves the information even when your computer is turned off.
Hard disk drive
Your
computer's hard disk drive stores
information on a hard disk,
a rigid platter or stack of platters with a magnetic surface. Because hard
disks can hold massive amounts of information, they usually serve as your
computer's primary means of storage, holding almost all of your programs and files.
The hard disk drive is normally located inside the system unit.
CD and DVD
drives
Nearly all
computers today come equipped with a CD or DVD drive, usually located on the
front of the system unit. CD drives use lasers to read (retrieve) data from a
CD, and many CD drives can also write (record) data onto CDs. If you have a
recordable disk drive, you can store copies of your files on blank CDs. You can
also use a CD drive to play music CDs on your computer.
DVD drives
can do everything that CD drives can, plus read DVDs. If you have a DVD drive,
you can watch movies on your computer. Many DVD drives can record data onto
blank DVDs.
Floppy disk
drive
Floppy disk
drives store information on floppy
disks, also called floppies or diskettes. Compared to CDs and DVDs,
floppy disks can store only a small amount of data. They also retrieve
information more slowly and are more prone to damage. For these reasons, floppy
disk drives are less popular than they used to be, although some computers still
include them.
Why are
floppy disks "floppy"? Even though the outside is made of hard
plastic, that's just the sleeve. The disk inside is made of a thin, flexible
vinyl material.
2. Mouse
A mouse is a
small device used to point to and select items on your computer screen.
Although mice come in many shapes, the typical mouse does look a bit like an
actual mouse. It's small, oblong, and connected to the system unit by a long
wire that resembles a tail. Some newer mice are wireless.
A mouse
usually has two buttons: a primary button (usually the left button) and a
secondary button. Many mice also have a wheel between the two buttons, which
allows you to scroll smoothly through screens of information.
When you
move the mouse with your hand, a pointer on your screen moves in the same
direction. (The pointer's appearance might change depending on where it's
positioned on your screen.) When you want to select an item, you point to the
item and then click (press
and release) the primary button. Pointing and clicking with your mouse is the
main way to interact with your computer.
3. Keyboard
A keyboard
is used mainly for typing text into your computer. Like the keyboard on a
typewriter, it has keys for letters and numbers, but it also has special keys:
·
The function
keys, found on the top row, perform different functions depending on
where they are used.
·
The numeric
keypad, located on the right side of most keyboards, allows you to enter
numbers quickly.
·
The navigation
keys, such as the arrow keys, allow you to move your position within a
document or webpage.
You can also
use your keyboard to perform many of the same tasks you can perform with a
mouse.
4. Monitor
A monitor displays information in
visual form, using text and graphics. The portion of the monitor that displays
the information is called the screen.
Like a television screen, a computer screen can show still or moving pictures.
There are
two basic types of monitors: CRT (cathode
ray tube) monitors and LCD (liquid
crystal display) monitors. Both types produce sharp images, but LCD monitors
have the advantage of being much thinner and lighter. CRT monitors, however,
are generally more affordable.
LCD monitor (left); CRT monitor
(right)
5. Printer
A printer
transfers data from a computer onto paper. You don't need a printer to use your
computer, but having one allows you to print e‑mail, cards, invitations,
announcements, and other materials. Many people also like being able to print
their own photos at home.
The two main
types of printers are inkjet printers and laser printers. Inkjet printers are
the most popular printers for the home. They can print in black and white or in
full color and can produce high-quality photographs when used with special
paper. Laser printers are faster and generally better able to handle heavy use.
Inkjet printer (left); laser printer
(right)
6. Speakers
Speakers are
used to play sound. They may be built into the system unit or connected with
cables. Speakers allow you to listen to music and hear sound effects from your computer.
7. Modem
To connect
your computer to the Internet, you need a modem. A modem is a device that sends and receives computer
information over a telephone line or high-speed cable. Modems are sometimes
built into the system unit, but higher-speed modems are usually separate
components.
Cable modem
8.
Webcam
A webcam is a video
capture device connected to a computer or computer network, often using a USB
port or, if connected to a network, ethernet or Wi-Fi.
9. Software
Software is a general
term for the various kinds of programs
used to operate computers and
related devices. (The term hardware describes the physical aspects of
computers and related devices.)
Software can be
thought of as the variable part of a computer and hardware the invariable part.
Software is often divided into application software (programs that do work users
are directly interested in) and system software (which includes operating
systems and any program that supports application software). The term middleware is sometimes used to describe
programming that mediates between application and system software or between
two different kinds of application software (for example, sending a remote work
request from an application in a computer that has one kind of operating system
to an application in a computer with a different operating system).
Some general
kinds of application software include:
·
Productivity software, which includes word processors, spreadsheets, and tools
for use by most computer users
·
Presentation software
·
Graphics software for graphic designers
·
Specialized scientific applications
·
Vertical market or industry-specific
software (for example, for banking, insurance, retail, and manufacturing
environments)
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