Another reason for the advancement of touch screen technology is trying to provide a more natural user interface and similar productivity on smaller devices, which would be infeasible if a keypad is used.
The Although huge advancement are made in touch screen technology, they do suffer some various drawback similar to mouse and keyboards. Such drawbacks may result in injuring the user if not user properly. For example in the paper [http://www.ergonomic-solutions.net/pdf/Touch_Screen_Ergonomics_06.pdf "Ergonomics of Touch Screens"], "the general rule of thumb for a display only machine is to locate the machine in the “optimal viewing area”. However, with a touch screen, not only do optimal viewing area need to be considered, but also the arm position of the users. Without proper screen positioning, repetitive use of touch screen technology can lead to tendonitis, tenosynovitis and carpal tunnel syndrome. In a standing workstation, the upper arms of a user should be in a neutral posture, beside the torso. To accommodate most users, this should be about 105cm – 140cm off the ground. Due to the characteristics of LCD monitors, users that operate a touch device without a proper angle with experience fuzziness and distortion to characters. The optimal viewing angle for any LCD surface is between 30 to 45 degrees". [http://www.ergonomic-solutions.net/pdf/Touch_Screen_Ergonomics_06.pdf "Ergonomics of Touch Screens"]
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