what is PLC programs, SCADA systems?

Answer 1

A programmable logic controller is a specialized industrial computer that is optimized to run logical and math programs to control machinery and processes. It was designed to be easy to program (no special program skills needed) and it is easy to connect and troubleshoot. It can run in factory environments or outside in a metal box under the sunshine. It uses robust communications networks to tie PLCs together from all over the factory.

Supervised Control and Data Acquisition (SCADA) is a human interface program that displays the status of control in a factory or a process. It takes data from PLCs that are networked to its communication and shows the state as animated colored pictures of the equipment with words like "RUN" or "FAIL" popping up when there is a problem or a temperature gage that moves up its reading like a thermometer as the temperature rises. It includes pictures of knobs and push buttons that can be clicked by operators to turn on/off and adjust settings.

Answer 2

SCADA = Supervisory Control And Data Acquisition.
a large scale computer system (usually distributed) used to control and monitor industrial processes in a larger factory or manufacturing plant. For example a refinery, mill or generation plant.

PLC = Programmable logic controller
a specialized computer system used for control of industrial processes or machines in a factory. For example controlling a production line.