IoC is a design methodology used to build a loosely coupled system in software engineering by inverting the control of flow from your main program to some other entity or framework.

Here, the control refers to any additional activities a program is handling other than its main activities, such as creating and maintaining the dependency objects, managing the application flow, and so on.

Unlike procedural programming style, where a program handles multiple unrelated things all together, IoC defines a guideline where you need to break the main program in multiple independent programs (modules) based on responsibility and arrange them in such a way that they are loosely coupled.

In our example, we break the functionality into separate modules. The missing part was how to arrange them to make them decoupled, and we will learn how IoC makes that arrangement. By inverting (changing) the control, your application becomes decoupled, testable, extensible, and maintainable.