Problems of control and automation, help please!!! 2. What are the 4 classes of programming languages of PLC? 3. How to illustrate the meaning of control system in control and automation system? 4. How to illustrate the major role of CPU in a PLC and what is the major role of CPU? 5. How to illustrate the major role of volatile memory and non-volatile in a PLC and what is the major role of volatile memory and non-volatile? 6. An on-off controller is used to control the temperature of a process. The cycling amplitude is reduced by making the two heating rates very close to average required for normal operation. What are the disadvantages on this set up? Q2, Q4-Q5<= I can't find the relative answers from the Internet. Q6) Is it there will cause danger on disadvantage？ Because these are not calculation, I can't show the step and I don't know how to show it. Thanks.