C++ Constants Explained: When to Use #define, const, and constexpr

A technical guide published on DEV Community breaks down the three main ways to define constants in C++: #define, const, and constexpr. The #define preprocessor directive, often taught in introductory courses, is discouraged in modern C++ production code due to its lack of type safety, scoping, and poor debuggability. The const keyword is a true C++ language feature that enforces immutability while respecting the type system and scope rules, and can handle both compile-time and runtime values. Introduced in C++11, constexpr is the most powerful option, forcing the compiler to evaluate expressions at compile time and reducing computational cost for end users. The article also covers advanced constexpr features such as constexpr functions, if constexpr for compile-time branching, and static assertions for stricter template usage.