Visual Basic .NET is a radical departure from the previous versions of Visual Basic,the world’s most popular programming language. If you have had experiencewith Object-Oriented (OO) languages like Java or Delphi you will probably take to Visual Basic .NET fairly quickly. After you have spent a few months using VisualBasic .NET, you’ll find it hard to return to an earlier version (unless you really must). You have probably also read or heard that support for the common language runtime (CLR) and the .NET Framework transforms Visual Basic .NET into a “pure” or “true”object-oriented language. To decide how true this claim is, let’s first understand what a“pure” and “true” OO language is. If you are new to object-oriented software development, this chapter will introduce you to the OO concepts that all Visual Basic programmers need to know. This chapterintroduces these software developments and OO concepts early on, to help you derivethe most benefit from this book and from Visual Basic .NET. We begin by reviewing the evolution of software development over the past few decades. Then we shall see how Visual Basic .NET—hereon referred to as Visual Basic—has risen to meet the challenges of a demanding industry, answering the world’s thirstfor software.