Republic of Uzbekistan Ministry of Higher and Secondary Special Education Samarkand State University Faculty of International Educational Programs Department of Computer Science and Programming Technologies independent work

COMPUTER SYSTEM
A computer system is an electronic system consists of many parts works together to make the computer work. Computers work mainly to perform a specific task given by the user.
In a desktop computer, we see three parts of the computer such as input unit (keyboard and mouse), output unit (monitor and printer), and system unit (rectangular box).
In a laptop, all the parts of a computer are embedded on a single place. Hence, it is easy to carry them from one place to another place. Instead of using mouse, we use touch pad in laptops.

Important components of computer system

Generally, a computer system consists of four important components:

• 
  Input unit
  
• 
  CPU (Central Processing Unit) 
  
• 
  Output unit
  
• 
  Memory unit
  

Input unit

An input unit consists of input devices such as keyboard, mouse, scanner, and joystick. Input devices are used to send data to the computer.
An input device accepts the instructions and data from the user and converts it into the form, which is understandable to the computer. The converted data is send to the CPU (Central Processing Unit) for further processing. The various input devices include:

• 
  Keyboard
  
• 
  Computer mouse 
  
• 
  Scanner
  
• 
  Joystick
  

Keyboard

The name itself suggests that it is a board consists of arrangement of keys. It is the main input device for most of the computers.
Keyboard is an input device used mainly for entering symbols like letters and numbers into a computer. Input is entered into the computer by pressing buttons or keys.
Generally, it is used for typing text and numbers on ms word, note pad, and other programs. Keyboards are also used for playing games.

A keyboard consists of several keys on which alphabets, numbers, and some other symbols are printed. To enter any text into the computer we press alphabetic keys whereas to enter numbers into the computer we press numeric keys. Most of the keyboards are generally attached to a computer via USB port. The keys or buttons of the keyboard is made of plastic.
Like the keyboards on a typewriter, computer keyboards have keys for numbers and letters. However, computer keyboards also have special keys.
The function keys are found on the top of a computer keyboard. The function keys of a computer keyboard include F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12. They perform different functions depending on where they are used. For example, Microsoft Windows users can use Alt+F4 to close the current program or shutdown the computer. F1 is used as the help key. When the user press F1 button a help screen is opened. Similarly, other function keys are also used for various purposes.

Computer mouse

A computer mouse is an input device used for selecting items, opening, and closing items, copying and deleting the items on the screen by controlling the movement of a cursor or pointer on the computer screen. It is also used for creating new folders and browsing internet.

The mouse turns the movement of the hand (left, right, forward, and backward) into equivalent electronic signals that in turn are used to move the pointer. When you move the mouse with your hand on a surface, a cursor or pointer on the computer screen also moves in the same direction. For example, if we move the mouse towards right side, the cursor on the computer screen also moves towards right side. In the similar way, if we move the mouse towards left side, the cursor on the computer screen also moves towards left side.

Scanner

Scanner is an input device used mainly for capturing the printed documents and uploading it into computer as digital images. These digital images are easily viewed and edited on computer. A scanner can be connected to a computer via USB or SCSI.