Why is an object's internal data usually hidden from outside code?

Encapsulation is one of the fundamental principles of object-oriented programming that focuses on combining the data and methods acting on the data into a single unit called an object. The intention behind encapsulation is to bundle the data, or state, and methods, or behavior, in such a way that the internal workings of the object are hidden or unknown to other parts of the program.

Data hiding is a technique used in encapsulation where the internal data or state of an object is not directly accessible from the outside. Instead, access to the internal data is restricted and regulated via methods or functions that are specifically provided by the object to interact with the data. These methods or functions are called accessor methods (like getters and setters) and are used to read, write, or manipulate the object's internal data.

There are several benefits associated with hiding an object's internal data from outside code, some of which include: 1. **Controlled Access**: By hiding the internal data and using accessor methods, control over who can access or modify the data can be better maintained. This helps to maintain the integrity and consistency of the object's state. 2. **Modularity**: Encapsulating data into objects makes the code more modular and easier to debug, maintain, and understand. Each object has a specific responsibility, making it easier to track down errors and focus on specific parts of the code. 3. **Easier to Change**: When internal data is hidden, changes in the object's implementation are less likely to affect other parts of the program, as they only interact with the object through its well-defined interface. This allows for easier updates and extensions to the code in the future. 4. **Reduced Complexity**: Data hiding reduces the complexity of the code, as the interactions between objects and their states are clearly defined and separated, making it easier to reason about the behavior of the program. In conclusion, an object's internal data is hidden from outside code primarily for modularity, controlled access, ease of change, and reduced complexity. These principles increase the robustness, maintainability, and extensibility of software built using object-oriented programming principles.