Owing to the rapid progress in computer and information
technology, the computers these days have become able to carry
out many complex tasks that only the human did in the past. But
as for the interface between human and computer, it is still
difficult for common people to handle, unless he is very
familiarized to use computer. Average person has to make great
effort to handle keyboard of character user interface (CUI), and
although the graphical user interface (CUI) becomes more easy
than CUI with a mouse to select menus on the display, CUI is
still difficult for average person. Especially for the interface of
CAI system which is ordinary a tool for educating people, it is
more important to make more learned and knowledgeable by
using CAI