Which of the following is NOT one of the four main principles of object-oriented programming?

The principle that is NOT one of the four main principles of object-oriented programming is iteration. The four primary principles of object-oriented programming are encapsulation, inheritance, polymorphism, and abstraction.

Encapsulation refers to the bundling of data and methods that operate on that data within a single unit, typically a class. This principle helps in restricting access to certain details of an object, promoting modularity and reducing complexity.

Inheritance is a mechanism where a new class can inherit characteristics and behaviors (methods) from an existing class, allowing for code reusability and the establishment of hierarchical relationships between classes.

Polymorphism allows methods to do different things based on the object it is acting upon, facilitating flexibility and the ability to process objects differently depending on their data type or class.

Iteration, while an important concept in programming such as looping through collections or performing repetitive tasks, does not pertain specifically to the object-oriented programming paradigm and thus is not considered one of its foundational principles.