I. Introduction
Virtual keyboard [1] [2] [3] is one of most primitive alternative text entry mechanism [4] [3] for entering text. It replaces the hardware keyboard through on screen character image map. It is a challenging task to arrange large number of keys of hardware keyboard into small hand held device interfaces. Special helping mechanisms like word completion [5], word prediction [6], adaptation and personalization [7], can also be easily incorporated with virtual keyboard to increase the user performance, which are found to be difficult to integrate into hardware keyboard. These above mentioned scenarios are the cause of the virtual keyboard design as a explorable field in present days to reduce gap between man and machine.