Components of computer A computer consists of three units. These units are as follow: 1. Input unit: This unit is responsible for taking data from user and then forwards it to next unit (System unit) for processing. The devices which come under this unit are keyword, mouse, joystick and many more. 2. System unit: This unit is also called as the brain of the system. The main component of this unit is the microprocessor which is responsible for overall functioning of computer. This unit also contains computer circuits and memory chips to store the information or data for future use. 3. Output unit: This unit is responsible to display the output according to user's input. This unit takes data from system unit. The devices which come under this unit are monitor, printer and many more. Hence, the case that holds a computer's circuitry and storage devices is called a System unit.

Turn on/off computer It is better to use shut down option present in startup menu instead of using on/off switch to turn on/off the computer. It is because if user uses the shutdown option then before the computer gets switched off, all the files of computer get safely stored in the computer. If user uses on/off switch to turn on/off the computer then it is possible that some files get lost during switching off the computer. Due this it is possible that user can face problem when next time he tries to switch on the computer. Sometime it may be possible that the computer will not get turn on next time. Hence, the statement "Instead of using the on/off switch to turn off a computer, you should instead use the Shut Down option from the Start menu or Apple menu" is img .

Mac operating system Macintosh is also an operating system like window. Microsoft is the creator of window operating system similarly apple launches Macintosh operating system for apple computers. In windows some frequently used program icons like internet explorer, window media player are present at their task bar. Similarly, Macintosh displays a row of frequently used program icons at the bottom of the screen. This row is called as dock. The main motive behind to add dock in mac is to make Mac OS more user friendly and conveniently for user. So that whenever he wants to play music or want to browse web page there is no need to click on apple icon and then find program and execute it. A user can directly select it from dock icon. A user is also allowed to add or remove icon from dock according to their needs. Hence, On the Mac desktop, the dock displays a row of program icons.