What is the definition and format of call function in C language?

Function definition and call format: Function definition: return_type function_name(parameter_type parameter1, parameter_type parameter2, ...) { ... //Function body// ... return value; } Function call: function_name(argument1, argument2, ...);

C language function, this thing is simple and simple, but complicated, it can also be a bit of a mess. Let's get straight to the point and answer your question first: What is the format of function definition and call?

Defining a function is like building a house for it. It must have a house number (function name), a room (function body), and also explain what the house is used for (return value type), and what is needed to move in (parameter list). Therefore, the standard format looks like this:

 <code class="c">return_type function_name(parameter_type parameter1, parameter_type parameter2, ...) { // 函数体，也就是干活的地方// ...一堆代码... return value; // 返回值，如果函数有返回值的话}</code>

return_type specifies what type of data the function returns, such as int , float , char , or void means that no value is returned. function_name is the name of the function, which must comply with the naming rules of C language. You cannot use keywords, so it is best to know the name. parameter_type , parameter1 , parameter2 and other parameters are the parameter types and names of functions. They can have multiple parameters or no parameters. The part enclosed in {...} is the function body, which writes the code you want to execute. return value is the return value of the function. If return_type is not void , there must be a return value.

Calling a function is like when you go to live in that house, you have to know the house number (function name), and you have to prepare the corresponding "baggage" (parameters). Call format:

 <code class="c">function_name(argument1, argument2, ...);</code>

function_name is the function name you want to call, argument1 and argument2 are the parameters passed to the function, and the type must match the parameter type in the function definition. If the function has a return value, you can assign the return value to a variable, or use the return value directly.

This seems simple, but there are many pitfalls hidden inside. For example, is the method of parameter passing, is it a value passing or an address passing? This directly affects whether the modification of parameters inside the function will affect external variables. When passing the value, the function internally modifies a copy of the parameters, and the external variables are not affected; when passing the address, the function internally modifies the external variable itself. This has to be chosen according to the actual situation. If you use it wrong, the bug will come, making you suspicious of your life.

For example, if the recursive call of a function is not handled properly, it is easy to cause stack overflow and program crash. Also, although the function prototype declaration looks inconspicuous, if it is not declared correctly, the compiler may report an error or some unpredictable errors.

Finally, what I want to say is that when writing functions, you must pay attention to the readability and maintainability of the code. The function should be single, and do not write it as a "hodgepodge"; the function should be as few as possible, and do not exceed five; the function comments should be written clearly to facilitate others (and to your future understanding). This seems to be a detail, but these details determine the quality of your code and the efficiency of your future maintenance code. Don’t think it’s troublesome. These good habits can help you avoid many detours. Remember, writing code is not only to make the machine understand, but also to make people understand.

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