Is there is somehow I can develop application(in 7650) for inserting a new writing language to T9 predictive input ? I already found that there'll a file in c:\system\data\ to keep the new insertion word , but I don't know the format, can anyone can give me the spec of the file ?
This is a Tegic proprietary format! I would be very surprise if they would give you its detail since the compression technique used to represent each language is a key technology for them and they would probably not like competitors like Zi having access to it.
Anyway the file you found is probably the user database which probably has a limited size and is active in addition to the selected dictionnary => it may be useful to add some specific words by yourself, but definitely not a full language!