Programmable Timer Switch per the definition by National Electrical producing Association, a PLC is defined as “A digitally operating electronic apparatus that uses a programmable memory for the internal storage of instructions by implementing specific functions such as logic sequencing, timing, counting, and arithmetic to regulate, through digital or analog input/output modules, numerous types of machines or processes”.Initially PLC was invented to fulfill the growing wants of the automotive manufacturing business. Before advent of PLC, the complex industrial process was controlled by lots of relays,dedicated closed loop controllers,drum sequencers and cam timers. The task of updating such huge control system was terribly cumbersome and expensive. to overcome these shortcomings, digital laptop was employed to control the economic control process. GM Hydramatic, the automatic transmission division of General Motors, was the first company to concern a young to exchange its arduous wired relay system in 1968. Bedford Associates won the bid and created the first PLC within the market. it was named 084, since it absolutely was the 84th project of Bedford Associates. Since then thousands of PLCs are launched in the market. All the manufacturers of PLCs give in depth network support to their clients.The objective of the earlier version of PLCs was to replace the relay logic systems. A programming language referred to as Ladder Logic was used to program those devices. Ladder Logic described the perform by a graphical drawing of the circuit diagrams of the relay logic hardware. Later, several other ancient programming languages like Basic,C,etc. were developed to program the PLCs. except traditional programming languages, state transition diagram based mostly languages like State Logic is also used widely. Branded programming terminals were used to program the earlier versions of PLCs till the mid Nineteen Eighties. nowadays application software on PCs will directly program the PLCs through RS232,RS422,RS485,Ethernet ports. assistance of a laptop support supplier might be taken to diagnose any downside in communicating with the PLCs through ports.PLC is the main element of any method control system. Multiple PLCs can be connected to the most laptop to regulate complicated processes like motion control, distributed management system, networking, method control, sequential relay management,etc. In terms of communication, storage, information handling and processing capabilities, some of the most recent PLCs could compete against a la mode PCs. because of the extensive input/output design, PLCs might be connected to sensors and actuators while not abundant hassle. Through sensors, PLCs might monitor method variables like pressure,temperature, switches position,etc. Magnetic relays,solenoids, pneumatic cylinders, electrical motors might be controlled by the PLCs through actuators. For debugging the sensor and actuator problems, intensive network support is provided by the manufacturers of PLCs.