How do I convert a DOS file into a Windows program?
Unfortunately, not very easily. While DOS programs will run under Windows and you may also want to look into Windows console applications (which act pretty much like a DOS application running under Windows), the structure of a Windows application is very, very different from a DOS application.
DOS applications can use a variety of methods to get input from the user and to display information back. In Windows, you create a window and associated window procedure and your application has a main loop that calls GetMessage() and a few others, which direct various events to your window procedure. This process of only running code in response to the window procedure being called is referred to as event-driven programming.