advanced concepts of oops

Early binding means that the address to be called when calling a function is statically known at compile time. Late binding means that the address of the function is calculated at runtime.

For a non-oo example something like this might explain it.

#include <iostream>

using namespace std;

int foo() {
	return 100;
}

int bar() {
	return 200;
}

int early_binding(bool b) {
	// Early binding knows the address of the function
	switch(b) {
		case true: return foo();
		case false: return foo();
		default:
			throw exception("well this is unlikely");
	}
}

int late_binding(int (*p)()) {
	return p();
}

int main() {

	cout << "early: " << early_binding(true) << endl;

	// Late binding looks up the actual function to call at runtime
	cout << "late : " << late_binding(true ? foo : bar) << endl;

    return 0;
}

For a OO-example, a virtual class member means that the lookup of the method address has to use the v-table, this leads to late binding (depending on the how the instance is "held");

#include <iostream>

using namespace std;

class base
{
public:
    base() { }
    virtual ~base() { }

    virtual int foo() { return 100; }
};

class a : public base
{
public:
    a() : base() { }
    virtual int foo() { return 200; }
};

int main() {

    base* x = new a();

    // Late binding, v-table is used to lookup correct implementation;
    cout << "Late: " << x->foo() << endl;

    return 0;
}

Hope this helps,
Fredrik