From this, we can say that plc is generally a digital computer which builds for controlling the machine.

Different from our personal computer it prepared for according to industry working situations and it consists of special input and outputs and its special programming language.

At its creation time, it was considered the replacement of relay but due to many functional capabilities, it started working in numerous complicated industrial submissions.

As its construction is the same as the computer, it has ability to work not only for relays switching but also perform many applications like time calculation, counting, comparison, and processing of different analog signals.

Plc has numerous benefits over a conservative relay using controlling. Relay uses many wiring but plc avoids wiring system and relay can be used only for single or specific function but plc performs many functions.