Input Devices
An input device is any device that is used to supply information to a computer. A few examples of input devices are given below.
Keyboard
The most common input device is the keyboard, which is used both for text-based data input and for selecting commands.
Keyboards usually have the following:
- Keys for the letters of the alphabet.
- Keys for punctuation symbols.
- Numbered keys or a numeric keypad (or both).
Standard keyboard
- Keys to move the typing cursor and other text controls, such as Tab, Insert, Delete, Backspace, Enter, and so on.
- Keys which change the function of other keys, such as Shift, Caps Lock, Alt, and Ctrl.
- Function keys numbered from F1 to F12. The function of these keys is set by whichever program is running.
Mouse
Computers are usually operated through a graphical user interface. This means that the user selects a command from the computer's screen display by moving a pointer and clicking an icon.
A mouse is the device usually used to control the movement of the pointer on the screen.
- A mouse is used by moving it across a mouse mat or other flat surface. This moves a ball on the bottom of the mouse. The movement of the ball sends a signal to the computer. Software interprets this signal and performs an operation, such as moving a cursor or drawing a line.
- A mouse has two or more buttons on top of it, the function of which depend upon the software being used.
Microsoft mouse
Trackball
- A trackball can be used as an alternative to a mouse. It has buttons, like a mouse, but the pointer is moved using a rotating ball set into the top of the device (basically an upside-down mouse).
- Some people find a trackball easier to use than a mouse. One advantage is that it does not need a flat area to use it. For this reason, trackballs are sometimes included on laptop computers.
Touch Pad
- A touch pad is another device for moving the pointer. In this case, you use your finger or a pen-like instrument (or stylus) on a sensitive pad to move the screen pointer.
- Because a touch pad is flat and does not require the user to push down a specific key (as with a keyboard) or grasp it (as with a mouse), it is often used as an input device for people with particular disabilities. Touch pads are also used on laptops and palmtop computers.
- Another form of touch pad is the graphics tablet. This enables the user to create an image on the computer by drawing on the pad with a specially designed pen. Graphics tablets are used by graphic design artists and for children's drawing software.
Light Pen
- A light pen is a hand-held device (very similar to a standard ballpoint pen) that has a device at the tip, which either emits light or is light sensitive. The user is able to send information to the computer by touching the pen onto certain areas of a specially designed screen.
- Light pens are not widely used because they require a lot of arm movement, making them tiring and uncomfortable to use.
- Possible uses include engineering production lines and science laboratories where dirt or other environmental factors make the use of a keyboard or mouse impractical.
Joystick
- A joystick consists of a base and a stick perpendicular to the base. The stick can be moved in any direction, enabling the user to move an object around the computer screen. A joystick can perform a similar function to a mouse or trackball, but is only commonly used for playing games.
Scanner
Scanners are input devices used to detect a pattern on paper (pictures or text) and then translate the pattern into computer data.
- Hand-held scanners are dragged across the paper to scan it.
- Flatbed scanners have the paper placed on top of them, in a similar way to a photocopier. These are more expensive than hand-held scanners but they are usually able to produce higher resolution images.
- Companies needing to store paper records can transfer them to microfilm. A microfilm is a series of page images, miniaturised onto 35mm film. Special scanners are available to prepare and read microfilm using a computer.
- If a scanner is used to scan a page of text, Optical Character Recognition (OCR) software can be used to convert the scanned image into text data that can be edited using word processing software.
Digital Cameras
- Digital cameras work in much the same way as normal cameras, except that the exposure from the subject is recorded onto light sensitive diodes not photographic film. The image is saved to a flash memory card (CompactFlash for example). Images can often be printed directly to a printer or displayed on a television or can be transferred to a computer (either by connecting the camera to a suitable port (such as a USB port) or by inserting the memory card into a card reader.
- There are also devices to capture moving images. Web Cams can record low resolution video images. High resolution digital video cameras are available, but are still quite expensive. Some filmmakers are starting to record motion pictures entirely on digital video.
