Benefits of pointers?

Question

I recently developed an interest in C programming so I got myself a book (K&R) and started studying.

Coming from a University course in Java (basics), pointers a

Answer 1

Ignore that answer please.

If you don't know how to use pointers, learn how to use them. Simple.

Pointers as you say allow you to pass more than one variable into a function via a pointer to it, as you have rightly observed. Another use of pointers is in referring to arrays of data, which you can step through using pointer arithmetic. Finally, pointers allow you allocate memory dynamically. Therefore advising you don't use pointers is going to severely limit what you can do.

Pointers are C's way to talk about memory addresses. For that reason, they are critical. As you have K&R, read that.

For one example of usage, see my answer to this. As I say in that answer, it isn't necessarily how you'd do it, given the question.

However, that technique is exactly how libraries like MPIR and GMP work. libgmp if you haven't met it powers mathematica, maple etc and is the library for arbitrary precision arithmetic. You'll find mpn_t is a typedef to a pointer; depending on the OS depends on what it points to. You'll also find a lot of pointer arithmetic in the slow, C, versions of this code.

Finally, I mentioned memory management. If you want to allocate an array of something you need malloc and free which deal with pointers to memory spaces; specifically malloc returns a pointer to some memory once allocated or NULL on failure.

One of my favourite uses of pointers yet is to make a C++ class member function act as a thread on windows using the win32 API i.e. have the class contain a thread. Unfortunately CreateThread on windows won't accept C++ class functions for obvious reasons - CreateThread is a C function that doesn't understand class instances; so you need to pass it a static function. Here's the trick:

DWORD WINAPI CLASSNAME::STATICFUNC(PVOID pvParam)
{
    return ((CLASSNAME*)pvParam)->ThreadFunc();
}

(PVOID is a void *)

What happens is it returns ThreadFunc which gets executed "instead of" (actually STATICFUNC calls it) STATICFUNC and can indeed access all the private member variables of CLASSNAME. Ingenious, eh?

If that isn't enough to convince you pointers kinda are C, I don't know what is. Or maybe there's no point in C without pointers. Or...