Microsoft CodeView information screen
The CV file extension is primarily associated with a CodeView file. CodeView was a debugger developed in 1985 by David Norris at Microsoft and included in the company's development toolset, as well as Visual Basic and other languages.
CodeView was a full-screen application, rather than command line-oriented, and included multiple windows that the user could view simultaneously and manipulate, including a command window for input and a code window for debugged code in the context of source code.
This 45-page document provides an explanation of The Art of Debugging.
See questions and answers about debugging on IT Knowledge Exchange.
SearchWinDevelopment.com offers a guide to testing and debugging.
Wikipedia has an entry about CodeView.