Hi guys. I have a question about file extensions. For example, if you create a .txt file, windows seems to know automatically that it is a file that can be opened by notepad or wordpad. It gives it a specific icon, and opens it inside notepad or wordpad. If I wanted to create a program that saved data in a file extension like .psh (my initials) I know I can do it. But exactly what do I need to code to make windows regonise the extension and give the file a particlular icon, and open up it up in my program etc? I guess one obvious thing is that my program must be able to recognise the file type and "decode" it.