Programmable logic controller

PLC
PLC stands for Programmable Logic Controller.PLC can be programmed and its data stores in non-volatile memory.(non volatile:Means data remains save in memory when power is suddenly off ).The main purpose of plc is to automized the industries that is now:it is possible to work without labour through your machine automatically,your machine should be connected with PLC.
The desired output can be taken by changing program through software that is installed in computer your computer must be connected with plc through data cable.PLC programming can be done through:
ladder logic
stl(statement list)
fbd(functional block diagram)

Ladder logic is famous :We called it ladder because it appearence looks like a ladder .
Vertical lines in ladder logic shows a power supply normally in dc 12 v or etc.Coil shows output and two small vertical lines shows a switch or input.