form. Example: Monitor, Printer etc. . .
. Memory Unit The Memory Unit is of two types which are primary memory and secondary memory. The primary memory is used to temporarily store the programs and data when the instructions are ready to execute. The secondary memory is used to store the data permanently.
The Primary Memory is volatile, that is, the content is lost when the power supply is switched off. The Random Access Memory (RAM) is an example of a main memory. The Secondary memory is non volatile, that is, the content is available even after the power supply is switched off. Hard disk, CD-ROM and DVD ROM are examples of secondary memory.
. . . Input and Output Devices Input Devices: ( ) Keyboard: Keyboard (wired / wireless, virtual) is the most common input device used today.
The individual keys for letters, numbers and special characters are collectively known as character keys. This keyboard layout is derived from the keyboard of original typewriter. The data and instructions are given as input to the computer by typing on the keyboard. Apart from alphabet and numeric keys, it also has Function keys for performing different functions.
There are different set of keys available in the keyboard such as character keys, modifier keys, system and GUI keys, enter and editing keys, function keys, navigation keys, numeric keypad and lock keys. Figure . Keyboard ( ) Mouse: Mouse (wired/wireless) is a pointing device used to control the Fingerprint Reader / Scanner is a very safe and convenient device for security instead of using passwords, which is vulnerable to fraud and is hard to remember. ( ) Track Ball: Track ball is similar to the upside- down design of the mouse.
The user moves the ball directly, while the device itself remains stationary. The user spins the ball in various directions to navigate the screen movements. ( ) Retinal Scanner: This performs a retinal scan which is a biometric technique that uses unique patterns on a person's retinal blood vessels. Figure .
Retinal Scanner ( ) Light Pen: A light pen is a pointing device shaped like a pen and is