Three ways, two legal one not. 1. Call the accessor function; 2. Make main a friend of the class and access the member directly. 3. Work out the address of the member and access its memory directly.
class PrivTestCls
	int a;
	int b;
	int c;

	PrivTestCls(int _a,int _b,int _c) { a=_a; b=_b; c=_c; }
	int get_a() { return a; }
	friend void privtest();

void privtest()
	PrivTestCls x(1,2,3);
	printf("a=%d\n",x.get_a()); // we can do this without being a friend
	printf("b=%d\n",x.b); // we can do this because we're a friend

	// this defeats private but the syntax makes it pretty obvious that's what's happening
	int *ptr2=(int*)&x;
In reality if your application design requires you to access c then you must create an accessor function or make the accessing function a friend. But if the class design prevents it then you will have to negotiate with the class designer; perhaps he can suggest an alternative design that doesn't require you to access the private data.