computing-pen / pen

Automatic computing-pen is a pen which will calculate
automatically on the basis of trace of writings.The pen is fixed with ordinary pen-core and can be used as sign pen.When the automatic computing-pen is used to write arithmetic expression,it will catch writing trace automatically.When the writing is finished,as long as you press the button,the inductor in the pen will calculate according to writing trace and then the projector will give you right answer.