Eddition of : ibadullah arife
In this article
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
called hardware. (Software, on the other hand, refers to the instructions, or
programs, that tell the hardware what to do.)
The following illustration shows the
most common hardware in a desktop computer system. Your system might 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.
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.
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.
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.
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; 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.
- If you have a recordable CD or DVD drive, periodically
back up (copy) your important files to CDs or DVDs. That way, if your hard
disk ever fails, you won't lose your data.
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 these disks are called
"floppy" disks? The outside is made of hard plastic, but that's just
the sleeve. The disk inside is made of a thin, flexible vinyl material.
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. For more information, see
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. For more information, see
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 the newer LCD (liquid crystal
display) monitors. Both types produce sharp images, but LCD monitors have the
advantage of being much thinner and lighter.
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
material. 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.
Speakers are used to play sound.
They can be built into the system unit or connected with cables. Speakers allow
you to listen to music and hear sound effects from your computer.
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.
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