The high-level language ST (Structured Text) provides all language elements as text commands. This enables wellstructured applications to be created.

The basic scope of commands includes:

• Commands for data management
• Arithmetic functions
• Control structures
• Commands for accessing I/O
• Communication functions
• Object-oriented programming according to IEC 61131-3 ED3

The addition of technology packages for Motion Control adds powerful, extremely flexible Motion Control commands to the instruction set (e.g.: _pos(...) for positioning axes). The system functions can be selected from a clearly arranged library and can be used in the ST source by means of drag & drop.

An ST source file basically consists of continuous text. This text can be structured by dividing it into sections. These sections represent logical units of an ST source.

These sections can be::

• a program that is assigned to a runtime level,
• a class with its subordinate methods,
• a function block with its own memory, or
• a function without its own memory

Function blocks, classes and functions are not allocated to a runtime level, but are instead called and supplied with parameters in programs.