I disagree. Just because your code has an interface doesn't make it OOP. If your functions are stateless yes they have an interface but that's not really OOP wh

I disagree. Just because your code has an interface doesn't make it OOP. If your functions are stateless yes they have an interface but that's not really OOP which is usually defined as scoped data bound with behavior. A bunch of static classes aren't OOP either, they may be using classes, but the state is global so it's not OOP. Interfaces are just one aspect of OOP and the concept of interfaces existed long before OOP and is used in other programming paradigms. An imperative program can have an interface too.