Which design principle emphasizes building a complex system from simpler components?

The design principle that emphasizes building a complex system from simpler components is composition. Composition focuses on constructing larger systems by combining simpler, reusable components or classes. This principle allows developers to create complex behavior and functionalities by assembling various smaller entities, rather than relying on a single, monolithic structure. It supports modular design, making systems easier to maintain, test, and modify over time.

For instance, in object-oriented programming, using composition involves creating classes that include other classes as part of their state. This approach promotes flexibility, as it enables the system to be composed of interchangeable parts, allowing for easier updates and enhancements without needing to alter the entire system architecture. By leveraging composition, developers can create scalable and maintainable applications that effectively encapsulate complex behaviors through well-defined interfaces and interactions among components.