CodeView was a standalone debugging-only application that originally shipped with Microsoft C++ v5.0 (6.0?) and earlier.
Upon the release of Microsoft Visual C++ 1.0, the functionality of CodeView was integrated into a single programming environment, known as the IDE or Integrated Development Environment. This integration is seen by many developers to be a more natural way of developing software since coding and debugging can be done without switching programs or context.
This integration is so popular that most development tools and/or platforms offer similar products or features. Today, the debugger is considered an integrated and essential part of the Microsoft Visual Studio family of products.