Difference between const. pointer and reference?

Question

What is the difference between a constant pointer and a reference?

Constant pointer as the name implies can not be bound again. Same is the case with the reference.

Answer 1

When you should use each:

reference: Use these by default. It is very common for people to dereference NULL pointers. You eliminate that risk with a reference.

const pointer: When you want a reference, but can't make one. For example, you are writing a driver, and you'd like a pointer to the beginning of a memory map. A reference doesn't make as much sense in that case. Also, if you need an array of the things, a reference won't work (though an array of simple classes with reference members will).

In the next example, a const pointer checks an error that a reference can't check:

int addFour( int* register ){
  if(isNull(arg)){
    throw NullPointerException();
  }  

  // some stuff
  *register += 4;

  return register;
}

// This could be any function that does pointer math.
bool isNull(const int* ptr){
  return( NULL == ptr );
}