A computer program for execution on a computing device is provided to cross-train students in language development skills such as letter-word correspondence, word recognition, vocabulary, and sentence and paragraph comprehension. An actuator system controls the position in the axial direction and two limitation bearings, determine the axial end positions of the rotor. A locking claw 5 formed on the locking arm 4 is once resiliently moved downward to pass through a locking claw 43 of the cooperating housing 41 and is then restored into an original posture to engage the locking claw 5 with the locking claw 43. Target finish dates are established for the displayed critical tasks and the displayed critical tasks are monitored. In one embodiment of the channel scanning method, a receive channel is switched at predetermined intervals, it is checked whether the broadcast contents of the channel being received currently, after the channel switching, will change within the scanning time period, and a time period for receiving the channel is prolonged, if the broadcast contents will change.