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What are the differences between pointer variable and reference variable in C++?

I got my head around pointers in C (the basics anyway) and started reading up on C++. The book I’m reading jumps straight into references, and looking in the index doesnt got on to pointers until later on.

In C, I thought if I wanted to do a pass by reference function I would have to use pointers as arguments,
e.g.

void swapAandB(int *A, int *B){

//do something
}

But the C++ book, decides to put references to the original variable into the function. e.g.

void swapAandB(int& A,  int& B){

 //do something
}

My C++ book hasn’t explained why we don’t use pointers as in C. So I’m a little confused. I guess my question is what’s going on here?

Answer 1

References are and additional mechanism that C++ provides compared to C. Using pointers in C++ is perfectly legal, so you could still define your first function unmodified:

void swapAandB(int *A, int *B){

 //do something
}

The main advantage that references offer over pointers is that it is not that easy to have the equivalent of a NULL pointer. But, references, both semantically and syntactically go well beyond this in shaping C++ features as a language. I think this will become clearer once you get more into the language. Anyway, you can try and read this paper about the difference between pointers and references.