C++ Headers and Namespaces: Why Include <iostream>?

This article explains the necessity of including the `<iostream>` header file and the role of namespaces in C++. The header file serves as a "manual" for the functions of the standard library. `<iostream>` contains declarations for input/output streams (`cout`, `cin`). To use input/output functions, this header file must be included first; otherwise, the compiler will not recognize `cout` and `cin`, resulting in errors. C++ uses namespaces to avoid name conflicts, with standard library functions located in the `std` namespace. There are two ways to use `cout` and `cin`: explicitly prefixing with `std::` (e.g., `std::cout`), or using `using namespace std;` to open the namespace. The former is safer, while the latter should be used cautiously to avoid header file conflicts. In summary, the `<iostream>` header file is a prerequisite for input/output functionality, and the `std` namespace avoids conflicts through isolation. The combination of these two ensures the program runs properly.