The abbreviation for PLC is Programmable Logic Controller. A PLC is a kind of computer that runs a tailor-made program, depending on the customer's demand.

Depending on the state of certain inputs, a PLC program will send the correct outputs. The program is cycled through (usually 100x per second). The state of the inputs is read at the start of the program and the outputs are controlled at the end of the program.

Inputs (or inputs) are all devices that provide information about parts of a machine. These can be push buttons or sensors (we call these digital inputs because they only have 2 states, namely 0 or 1), but also temperatures, humidity (we call this analog inputs).

Every PLC manufacturer usually has its own development software. At Beckhoff they have the Twincat environment. It is based on the CODESYS language. The latest variant is Twincat3 and is. The great power in this is the ability to use interfaces. But also to inherit bits of code.

A PLC program is usually written offline (without inputs/outputs). When the installation is finished, IO tests (Input/Output tests) are first performed to see that all IOs are connected correctly. The program is then tested and adjusted where necessary.