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.
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; 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.
Tip
·
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 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 these disks 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.
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.
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