Tell me about the grammatical rules of functions in C language

The function syntax rules of C language are composed of function declaration, function definition and function call. A function declaration is used to tell the compiler the name of the function, its return type and parameter types. The function definition provides the actual implementation of the function, which contains the execution steps of the function. A function call is a statement that calls a function in a program, which transfers control to the definition of the function, performs the operation of the function, and returns the result.