i. Direct device based control:

1. Touchscreen

• It allows direct control touches on the screen using finger.
• Early designs were rightly criticized for causing fatigue, hand obscuring the screen, hand off keyboard, imprecise pointing and eventual smudging of the display.
• Lift-off strategy enables users to point at a single pixel.
• The users touch the surface and then see a cursor that they can drag around on the display.
• When the users are satisfied with the position, they lift their fingers off the display to activate.
• It can produce varied display to suit task.
• They are fabricated integrally with display surfaces.

2. Stylus

• Stylus is popularly used in mobile devices such as tablets, palm pilot.
• They are based on touch screen technology. Users can write with a stylus for more natural handwriting and increased motion control but can also use a finger for quick selection.
• Like touch screens, stylus interfaces misbehaves when users touch the screen in two or more locations at once.

ii. Indirect device based control:

1. Mouse

a. Advantage

• Direct relationship between hand and pointer movement in terms of direction, distance and speed.
• Permit a comfortable hand resting position
• Selection mechanism are included on mouse
• Does not obscure vision of the screen

b. Disadvantage

• Movement is indirect in a plane different from screen.
• Requires hand to be removed from keyboard
• Requires additional desk space.
• May require long movement distance
• Requires a degree of eye-hand co-ordination

2. Joystick

a. Advantage

• Direct relationship between hand and pointer movement in terms of direction and speed.
• Does not obscure vision of screen
• Does not require additional desk space.

b. Disadvantage

• Movement indirect in plane different from users
• Requires hand to be removed from keyboard keys
• Requires different hand movement
• May be difficult to control
• May be fatiguing to use over extended time

• May be slow and inaccurate. . Guidelines:

• Screen objects should be at least ¾’’ x ¾’’

• Objects separation should be at least 1/8’’
• When using touch screen larger screen objects should always be provides to foster accuracy in use
• For keyboard provide acceleration, equivalents and window navigation through keyboard keys