How do computers work?

How computers and machines are able to work after some initial human intervention?

• Computers are able to solve numerous problems. What is the basic process of it? How they are able to work? We need to use some initial intelligence to make them work. After that they are able to work without any human intervention.   Similarly, how a industrial machine is able to work after just some initial human intervention. We can say that electricity drives these things. So my question is how electricity is able to make them work? What are the principles, concepts, laws for this.

• Answer:

  If you are talking about automation, then the equipment in question is guided by a PLC or programmable logic controller. It runs like any other computer program. It monitors some parameters according to input data, and notes their condition. It then runs an algorithm which may or may not change the outputs and therefore the behavior of the equipment. The PLC then looks at the new input data an runs its  algorithm again, in an unending loop. A very simply example of a PLC regulating a mechanical system is a home's HVAC system.