1. Computer :
A computer is a general purpose device that
can be programmed to carry out a finite set of arithmetic or logical
operations. Since a sequence of operations can be readily changed, the computer
can solve more than one kind of problem.
Conventionally, a computer consists of at
least one processing element, typically a central processing unit (CPU) and
some form of memory. The processing element carries out arithmetic and logic
operations, and a sequencing and control unit that can change the order of
operations based on stored information. Peripheral devices allow information to
be retrieved from an external source, and the result of operations saved and
retrieved.
The first electronic digital computers
were developed between 1940 and 1945 in the United Kingdom and United States.
Originally they were the size of a large room, consuming as much power as
several hundred modern personal computers (PCs). In this era mechanical analog
computers were used for military applications.
Modern computers based on integrated
circuits are millions to billions of times more capable than the early
machines, and occupy a fraction of the space. Simple computers are small enough
to fit into mobile devices, and mobile computers can be powered by small
batteries. Personal computers in their various forms are icons of the
Information Age and are what most people think of as "computers".
However, the embedded computers found in many devices from MP3 players to
fighter aircraft and from toys to industrial robots are the most numerous.
2. Parts of a computer :
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
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.
a) 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.
b) 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.
v 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.
v 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.
v 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.
v 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.
c) 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. For more information,
d) 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. For more information, .
e) 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.
f) 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.
g) 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.
h) 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.
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لا تنسوا العودة للصفحة الرئيسية لتصفح المزيد
من البحوث و الوثائق التعليمية.
ملاحظة: يرجى التبليغ عن أي رابط لا يعمل
و ذلك بترك تعليق أو مراسلتنا عبر بريد الموقع أو صفحتناعلى فيسبوك
كلمات دلالية: [ تحميل بحث الجغرافيا جغرافيا تلوث البيئة التلوث بيئي ثانوي متوسط أولى ثانية ثالثة رابعة ابتدائي مذكرات اتسطوانات بكالوريا البكالوريا دور جوان لغة عربية رياضيات تاريخ علوم طبيعية فيزياء فلسفة فرنسية انجليزية أدب علوم اسلامية شرعية ]
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ملاحظة: يرجى التبليغ عن أي رابط لا يعمل
و ذلك بترك تعليق أو مراسلتنا عبر بريد الموقع أو صفحتناعلى فيسبوك
كلمات دلالية: [ تحميل بحث الجغرافيا جغرافيا تلوث البيئة التلوث بيئي ثانوي متوسط أولى ثانية ثالثة رابعة ابتدائي مذكرات اتسطوانات بكالوريا البكالوريا دور جوان لغة عربية رياضيات تاريخ علوم طبيعية فيزياء فلسفة فرنسية انجليزية أدب علوم اسلامية شرعية ]