Learning C++ const Constants from Scratch: Definitions and Usage Scenarios

In C++, `const` constants are used to define fixed values to prevent accidental modification. The definition syntax is "`const data_type constant_name = initial_value;`". They must be initialized upon definition and cannot be modified (modification will cause a compilation error), with the same scope as ordinary variables. Key characteristics: non-modifiable, mandatory initialization, and the same scope rules as ordinary variables. Common scenarios include protecting critical data (e.g., class size, pi), improving code readability (replacing "magic numbers"), serving as array lengths (requires compile-time constants), and optimizing function parameters (`const` references avoid large object copying). Compared with `#define`, `const` offers safer type checking. Note: `const` constant values must be determined at compile time and cannot be assigned using runtime variables; their scope is determined by their definition location (local or global). `const` is an important tool for protecting data and enhancing code reliability.