Write a program to overload binary &&(logical and) operator using friend function.

Although this is OK as an exercise, overloading operator&& in real code is a bad idea. Say we have this:

if(f() && g()) {...}

The C++ standard says that if f() returns false, g() is not invoked (known as lazy evaluation). However, an overload of operator&& cannot duplicate this behavior. So if g() has side effects, the behavior will differ from what would otherwise have been the case.

It's the same with operator||: if the first expression is true, the second one isn't evaluated.