Keyboard
A computer keyboard is similar to a typewriter keyboard. It is an input device. Data can be entered into a computer through the keyboard. Usually it has 101 keys arranged in 5 groups
- Alphanumeric keys – in QWERTY layout (the first six letters on the top row of the letters are Q,W,E,R,T,Y) with A-Z ,0-9 plus some more characters.
- Modifier keys– In addition to letters and punctuation marks, the alphanumeric keys include the modifier keys as they are used in conjunction with other keys. E.g. Shift, Ctrl (control key), Alt (alternate key).
- Function keys– The function keys (F1, F2….F12) are usually arranged in a row along the top of the keyboard. They allow us to give the computer commands.
- Cursor movement keys- Arrow keys which let us change the position of cursor on the screen. In a word processing program, there is a mark on the screen where characters we type will be entered, this is called insertion point or cursor.
- Special purpose keys – Each of the special keys performs a specialised function.
- Esc– Key is used to back up one level in a multilevel environment, it can be used to close multiple opened programs in reverse order.
- Print screen – This key copies an image of the screen’s contents to the clipboard.
- Scroll lock – Scroll lock causes the cursor to remain stationary on the screen and the document’s contents move around it, as in MS-Excel.
- Pause– In some programs, the pause key can be used to stop a command in progress.
The numeric keypad usually located on the right side of the keyboard looks like an adding machine with ten digits and mathematical operators (+,-,/ and *).
Mouse
Mouse is a pointing device used to position the pointer. The pointer is an on-screen object usually an arrow, that is used to select a text, menus, move files or interact with programs, files or data that appear on screens. It also allows us to create graphic elements on the screens, such as lines, curves and freehand shapes. Clicking and drag-and-drop editing technique is used with the mouse. Earlier, ball-mouse connected via PS/2 port was used but now USB port connected optical mouse is prevalent.
Scanners
Image scanners
Image scanners convert any printed image into electronic image by shining light onto the image and sensing the intensity of the reflection at every point. Bar code reader is an image scanner.
Optical Character Recognition (OCR)
It is used to translate the image into text that we can edit. It uses specialized OCR software.
Optical Mark Reader (OMR)
These scanners are capable of recognizing a pre-specified type of mark made by pencil or pen. They are used in evaluation of answer sheets of objective test.
Magnetic Ink Character Recognition (MICR)
They are used in banking industry to process cheques. Cheques have bank identification code and cheque numbers in a special ink that is read by MICR devices.
Touch Screens, Voice Recognition Devices are also some of the input devices.
