Beginner's Guide to C++ Functions: Definition, Call, and Parameter Passing

This article introduces the core knowledge of C++ functions. A function is a "code utility" that encapsulates specific functionality, facilitating reuse and clear code structure. A function definition includes the return type, function name, parameter list, and function body, such as the `add` function for calculating the sum of two numbers. When calling a function, actual arguments must be passed, and the return value is received (use `void` if there is no return value). Parameter passing methods include value passing (the formal parameter is a copy of the actual parameter, and modifications do not affect the actual parameter), reference passing (using `&`, where the formal parameter is the actual parameter itself, and modifications affect the actual parameter), and default parameters (set from right to left to simplify calls). If a function is defined after it is called, a declaration must be provided first. Mastering these concepts enables code reuse and logical clarity.