Abstract: A lecture system is provided for the user to operate the teaching file on a display of an electronic device, the lecture system including a first sensor unit, a timer unit, a switch unit and a scroll unit. The first sensor unit is disposed corresponding to a first operating area; the timer unit electrically connects the first sensor unit and is installed with a threshold value; the switch unit electrically connects the timer unit and the first sensor unit for the user to switch between a first and a second input modes by operating on the first operating area for a first period of time less than the threshold value. The scroll unit electrically connects the timer unit and the first sensor unit for the user to scroll through the teaching file by operating on the first operating area for a second period of time longer than the threshold value.