Keyboard
The most common standard input device used for computers in keyboard. Both the data and programs can be inputted using keyboard and it is most useful for interactive dialogue. More like a typewriter it has all the alphabets, numerical and special characters found on a typewriter. Usually standard keyboards nowadays come with 100/102 keys which include the following 5 groups of keys.
- Alphanumeric keys
- Numeric keypad
- Function keys
- Cursor movement keys
- Modifier keys
- Special purpose keys
Keyboards based on different keys are as follows:
| 83 Keys | 84 – 100 Keys | 101/102 Keys | 104/105 Keys |
|---|---|---|---|
| Used in Extended Technology (XT) | Used in Advanced Technology (AT) | Used in Advanced Technology (AT) | Used in Advanced Technology Extended (ATX) |
| Function keys are not present. | Function keys are present from F1 to F10 | F1 – F10 Functions keys are present. | Function keys are present from F1 – F12. |
| Enter key is in small size, equal to all other keys. | Enter key is large. | Enter key is in such shape that it is vertical rather than horizontal. | Enter key is vertical rather than horizontal. |
| Caps Lock, Num Lock, Scroll Lock keys are not present. | Caps Lock, Num Lock, Scroll Lock keys are present. | Caps Lock, Num Lock, Scroll Lock keys are present and there are also present Page Up, Page Down, Home and End keys. | In addition to keys as in 101/102 keyboard there’s also two Win keys and a Menu key. Read More on Keyboard Layouts |
Keyboard internal circuitry has two main functions:
- It is responsible for sending the raw signal created by the key switches as they make electric contact and transferring them into a signal that can be sent to the PC.
- It handles the actual interfacing between keyboard and PC.
In keyboard, Typematic Delay is the time taken in milli-seconds to recognize the particular key when pressed. Minimum is 250 milli-seconds and maximum time is 1000 milli-seconds. Debouncing is used to clear the electrical signals on the row sensor and column sensor.
Computer Mouse
Computer mouse shown above has two buttons and a scroll wheel, which can also be used as a third button for advanced operations. The various operations that can be done using mouse include clicking, left-clicking, right-clicking, double-clicking, dragging and dropping. The left mouse key is used for selection if pressed once. When double clicked, it enters into a folder or opens a file. Whereas right mouse button when clicked gives the properties of the related item. Needless to say, click is pressing of mouse button once and double-click is pressing of mouse button twice quickly without moving the mouse.
Apart from these two standard input devices, some of the other widely used input devices include trackball, joystick, light-pen, touch-screen, scanner, digital-camera, microphones, bar-code reader, speech recognition, PC video camera and touch-pad.