LESSON 2 : INPUT DEVICES

What is Input?

Input Processing Output Storage

Types of Input

Data is the raw facts given to the computer.

Programs are the sets of instructions that direct the computer.

Commands are special codes or key words that the user inputs to perform a task, like RUN "ACCOUNTS". These can be selected from a menu of commands like "Open" on the File menu. They may also be chosen by clicking on a command button.

User response is the user's answer to the computer's question, such as choosing OK, YES, or NO or by typing in text, for example the name of a file.

Keyboard

The first input device we will look at is the Keyboard. The image used on the next page to illustrate the various keys may not look like the keyboard you are using. Several variations are popular and special designs are used in some companies. The keyboards shown below put the function keys in different places. The Enter and Backspace keys are different shapes and sizes. One has arrow keys while the other doesn't. It's enough to confuse a person's fingers!!

The backslash key has at least 3 popular placements: at the end of the numbers row, above the Enter key, and beside the Enter key. We also have the new Windows keyboards which have two new keys. One pops up the Start Menu and the other displays the right-click context sensitive menu. Ergonomic keyboards even have a different shape, curved to fit the natural fall of the wrists.

POINTING DEVICES

A variety of pointing devices are used to move the cursor on the screen. 
The most commonly used ones have two or three buttons to click and  for special functions.

Mouse	A ball underneath rolls as the mouse moves across the mouse pad. The cursor on the screen follows the motion of the mouse. Buttons on the mouse can be clicked or double-clicked to perform tasks, like to select an icon on the screen or to open the selected document. There are new mice that don't have a ball. They use a laser to sense the motion of the mouse instead. High tech!
	Advantage: Moves cursor around the screen faster than using keystrokes. Disadvantage: Requires moving hand from keyboard to mouse and back. Repeated motion can lead to carpal tunnel syndrome
Trackball	Instead of moving the whole mouse around, the user rolls the trackball only, which is on the top or side.
	Advantage: Does not need as much desk space as a mouse. Is not as tiring since less motion is needed. Disadvantage: Requires fine control of the ball with just one finger or thumb. Repeated motions of the same muscles is tiring and can cause carpal tunnel syndrome.
Glidepad	Uses a touch sensitive pad for controlling cursor. The user slides finger across the pad and the cursor follows the finger movement. For clicking there are buttons, or you can tap on the pad with a finger. The glidepad is a popular alternate pointing device for laptops.
	Advantage: Does not need as much desk space as a mouse. Can readily be built into the keyboard. Has finer resolution. That is, to achieve the same cursor movement onscreen takes less movement of the finger on the glidepad than it does mouse movement. Can use either buttons or taps of the pad for clicking. Disadvantage: The hand tires faster than with a mouse since there is no support. Some people don't find the motion as natural as a mouse.
Game Devices	Cursor motion controlled by vertical stick (joystick) or arrow buttons (gamepad)
	Advantage: A joystick gives a more natural-feeling control for motion in games, especially those where you are flying a plane or spaceship. Both have more buttons for special functions than a mouse and can combine buttons for even more actions. Disadvantage: More expensive Bulky Better ones require an additional peripheral card for best performance

Pen Input	Used esp. in Personal Digital Assistants (PDA) Pen Input is used for:
	Data Input - by writing. PDA recognizes your handwriting. (If only your friends could, too!) Pointing Device - Functions like a mouse in moving a cursor around the screen and clicking by tapping the screen. Command Gestures - You can issue commands by moving pen in patterns. So a certain kind of swirl would mean to save the file and a different kind of swirl could mean to open a new file.
	Advantage: Can use handwriting instead of typing Can use gestures instead of typing commands small size Disadvantage: Must train device to recognize handwriting. Must learn gestures or train device to recognize the ones you create Can lose the pen which is not usually attached to the device
Touchscreen	Make selection by just touching the screen.
	Advantage: It's natural to do - reach out and touch something. Disadvantage: It's tiring if many choices must be made. It takes a lot of screen space for each choice since fingers are bigger than cursors.
Digitizers and Graphics Tablets	Converts drawings, photos, etc. to digital signal. The tablets have special commands
	Advantage: Don't have to redraw graphics already created Disadvantage: Expensive

Now you are ready to proceed to the next lesson.