A keyboard includes a frame board, a base board secured to the frame board, a membrane circuit board in a space defined by the frame and base boards, a support board on the membrane circuit board, a switch board on the support board, keys on the switch board, a lithium battery on the base board, a control circuit board on the lithium battery, a projection device in the space defined by the frame and base boards, an outer screen on the right side of the frame board, an inner screen on the control circuit board, lights on the frame board, vent-holes on the frame board, first function keys and a second function key on the frame board, a recess on the right side of the base board with the lithium battery therein, a projection device below the vent-holes, and a projection hole aligned with the projection device.