Function return value is the value returned to you by the function you called. Such as void fun(int n, int m); The previous void shows that this function has no return value. Such as int fun (int m); When this function is executed, it will return an integer.

First, generally speaking, the default return value type of C language is int integer, and other functions can know what type the return value of this function is by looking at the type before its function. The return value is that the function is called and operated according to its passed-in parameters to get a final value, which is called the return value of the function.

Second, the function name of the function is not only the representative of the function, but also a variable. Because the function name variable is usually used to bring the processing result data of the function back to the calling function, that is, recursive call, it is generally called return value.

Third, a function can have a return value, as long as return can give one. But people usually don't use it for two reasons:

The return values in 1 and C/C++ are copied, but for large objects, the cost of copying is very high;

2. Some objects can't be copied-at least the compiler doesn't know how to copy them-such as arrays.