Ans : Keyboard.
Keyboard is a primary text input device. It comprises of a set of keys similar to a typewriter with addition of few extra keys for commands and additional numeric keypad. The standard arrangement of alphabetic keys is known as the QWERTY.
Working Of a Keyboard :
Each key send an electrical signal to the microprocessor. A standard keyboard includes about 100 keys and each key sends a different signal to CPU.
Classification Of Keys On a Keyboard :
1. Alphanumeric Keypad :
This keypad consists of numbers , alphabets and special characters like typewriter along with some special keys like ; Back space to delete a character , Caps lock to write capitals and enter key to run commands or go to next line.
2. Numeric Keypad :
It includes keys like a simple calculator from 0 – 9 , four basic operators ( + , - , * , / ) , decimal point and a Num lock key to activate / deactivate Numeric keys. When deactivated the numeric keys works like cursor movement keys.
3. Functions Keys :
The top most row of the keyboard with keys marked from F1 – F12 are called functional keys. These keys work as a short cut way to run commands without typing them. Each key has its own specific task.
4. Screen Navigation or Cursor Movement Keys :
Cursor control keys are used to move the cursor around the screen. Most keyboards includes the following Cursor movement keys.
a. Arrow Keys :
There are four arrow keys left , right , up and down keys. They are used to move the cursor one place left , right , up and down.
b. Home and End Key :
Home key moves the cursor to the beginning of the line while the End key moves the cursor to the end.
c. Page Up and Page Down :
These keys are used to make the cursor jump page by page. Page Up key is used to move to previous page while Page Down key moves the cursor to the next page.
5. Modifier Keys :
These keys are used to modify the input of other keys by holding them while pressing the other key.
Examples are Shift , Alt and Ctrl.
6. Special Keys :
In addition to these keys there are some special feature keys like ;
a. Delete Key : Used to delete a character.
b. Insert Key : Used to insert the text between already typed text without replacing it.
c. Esc Key : Its functions varies from program to program.
d. Print Screen Key : This is used to capture the displayed screen as an image.