This lecture focuses on the Iteration Protocol. We will explore the principles of operation by implementing the protocol in various ways, moving between imperative, object-oriented, and functional paradigms. Additionally, we will explore how different languages define and utilize iteration in their own ways, providing diverse perspectives and insights. Through this learning, you will understand that the iteration protocol is a common convention, unconstrained by specific languages or paradigms. Thanks to this characteristic, multi-paradigm programming, which blends different paradigms harmoniously, becomes possible. In addition to its multi-paradigm nature, the iteration protocol offers functional advantages such as improved computational and memory efficiency, and convenient type inference through lambda expressions, making it an inherently attractive concept. If your primary language supports generics, you can apply it anywhere, making it highly versatile and worth learning. We believe that both those familiar with OOP and those who have worked with FP will undoubtedly gain a new perspective by exploring the characteristics of iteration as explained in this lecture.