It's really important. Whenever we come to learn plc, our teaching assistants will ask students if they have an electrician foundation. If not, we must go and see "Learning the Preliminary Knowledge of PLC" newly published in Li Jincheng this year. This course is the basic knowledge of all brands of PLC learning. Even all the basic knowledge that digital industrial control technology must master, micro-class teaching, one knowledge point in each class, you can feel it.