C Functions: Step-by-Step Guide

In C language, the use of functions typically involves three steps: function declaration, function definition, and function invocation.

1. Function declaration: Before using a function, it is necessary to declare it in the code to inform the compiler of the function’s name, parameter list, and return type. Function declarations are typically placed at the beginning of the code file or before the function is called.

// 函数声明
int fun(int a, int b);

1. Function definition: After declaring a function, its specific implementation needs to be defined in the code. The function definition includes the return type, function name, parameter list, and function body.

// 函数定义
int fun(int a, int b) {
    return a + b;
}

1. Function call: When using a function, it is necessary to call the function in the code and pass the corresponding parameters. The function’s return value can be assigned to a variable when calling the function, or be directly used in an expression.

int result = fun(2, 3); // 调用函数并将返回值赋给result变量
printf("Result: %d\n", result); // 打印返回值

By following the three steps above, specific functions can be implemented using functions in the C language.