What is Structured Text Programming Language? Structured Text (ST) is a PLC programming language that resembles traditional programming languages like Python or Java and is based on text. It's not visual or graphics-based like ladder logic or Function Block Diagram. Using ST allows for efficient creation of large and complex PLC projects while maximizing memory allocation. It has its own advantages and disadvantages and can be a powerful tool in a programmer's toolbox. Start using Structured Tex