→Object-oriented programming 

according to Wikipedia (https://en.wikipedia.org/wiki/Object-oriented_programming): Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code: data in the form of fields (often known as attributes or properties), and code, in the form of procedures (often known as methods).
A feature of objects is that an object's own procedures can access and often modify the data fields of itself (objects have a notion of this or self). In OOP, computer programs are designed by making them out of objects that interact with one another. OOP languages are diverse, but the most popular ones are class-based, meaning that objects are instances of classes, which also determine their types. ...

If you want to use the logi.CAD 3 features for object-oriented programming according to the →IEC-standard, see the following articles about the possible ST-syntax:

• Page:Declaration of variables based on an interface

• Page:Declaration of a method

• Page:Declaration of a function block in ST

• Page:Declaration of an interface incl. method prototypes

• Page:Assignment attempt in ST