References to C + +

When the function parameter of C + + is a reference, it is the change of the original incoming parameter of the direct operation. Does not create a copy mechanism, does not stack into the stack operation. High efficiency, fast execution.

This differs from the parameter as a pointer. Although it can also manipulate the address of the original parameter, change its value, but the pointer variable is a copy mechanism, is passed into the stack, only the memory address pointed to the original variable address is the same. This will be a little less efficient.

The expression is fun (int &a, int &b);

If you do not want the fun function content to change the amount A, B needs to add the const modifier, such as fun (const int &a, const int &b)

References to C + +