What does the return value of the C language function mean? What decides?

C language function return value: The data returned to the calling code after the function is executed, and the type is determined by the function definition. 1. The return type is determined by the specification in the function declaration; 2. The function execution result is sent through the return value channel; 3. The return type must match the return type of the return statement; 4. Forgot or wrongly set the return value type, or not using the return statement will cause an error; 5. The return value type should be clear and clear to improve the readability and maintainability of the code.

C function returns value? This question is well asked! To put it bluntly, the return value of a function is a "gift" given to the code that calls it after the function finishes. What can this "gift" be? Integers, floating point numbers, characters, or even a more complex structure, or simply nothing - that's the void type.

What determines the return value type? When defining a function, you have to tell the compiler clearly: what gift this function wants to give. You have to write the return value type in the function declaration. For example, int add(int a, int b) means that the add function will send an integer. It’s like when you go to a restaurant to order food, and the menu says “Kung Bao Chicken Dice”, you will know that you want to serve chicken, not shredded pork.

So how does this return value work? Imagine that a function is like a black box, you throw the parameters in, it works hard and finally sends the result out through the return value channel. The code that calls the function is waiting to receive this "gift".

Take a chestnut:

 <code class="c">int max(int a, int b) { return (a > b) ? a : b; // 三目运算符，简洁明了！ } int main() { int x = 10; int y = 5; int bigger = max(x, y); // bigger 接收max 函数的返回值printf("The bigger number is: %d\n", bigger); // 打印结果return 0; // main函数也要返回值！ }</code>

Here the max function returns the larger of the two numbers. main function also returns an integer, usually 0 means that the program ends normally. This return value also plays an important role at the operating system level. The system will judge whether the program runs successfully based on the return value of main .

Let’s talk about the pitfalls. The most common pitfall is that you forget to write the return value type, or the return value type is written incorrectly. The compiler will report an error directly. Another pitfall is that the function clearly has a return value, but it does not use the return statement, or the return statement is written in the conditional branch, resulting in no return value in some cases, which will produce undefined behavior, the program may crash, or the running result may be inexplicable. There is another situation where the return value type does not match the type returned by the return statement, which can also lead to compilation errors or runtime errors.

Finally, a little personal experience: when writing a function, you must carefully consider the return value type and clearly express the function of the function. The return value is not only the carrier of the function result, but more importantly, it improves the readability and maintainability of the code. A well-designed function, the return value should be concise and clear, easy to understand and use. Don't think about doing too many things with the return value. It is best to do only one thing for a function, and a return value is enough. If you need to return multiple values, consider using a structure or pointer. Remember, clear and concise code is good code!

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