Over the past three decades, object-oriented programming (OOP) has created a fundamental shift in the way that programmers approach problems. In the early days of OOP, people involved in scientific computing could largely ignore object-oriented principles. Today, that is no longer the case. While the algorithms of scientific computing are still fundamentally procedural, the software packages are increasingly constructed in an object-oriented fashion. OOP allows scientific software to be more organized, easier to use, and more maintainable. In this section, you will learn how to use pre-defined objects in Sage. In Chapter 9, you will learn how to create custom objects.