When to use const and const reference in function args?

Question

When writing a C++ function which has args that are being passed to it, from my understanding const should always be used if you can guarantuee that the object will not be c

Answer 1

The main advantage of const reference over const pointer is following: its clear that the parameter is required and cannot be NULL. Vice versa, if i see a const pointer, i immedeately assume the reason for it not being a reference is that the parameter could be NULL.