Nothing. You have simply changed the extension. That won't change the file format. To do that you need to convert the file with conversion software.
Rename it with the proper extension. BAK files are created by some programs as back up versions of databases or documents in case something happens to the current version. If you sort by name in a directory, you'll find the .bak file right next to a file with the same name, only with a .doc or .ftm or some other extension. Give the file a 1 at the end of the name (Don't want to over write the current file) and change the extension and you'll be able to see what it is.
The .doc suffix at the end of Microsoft Word filenames is short for "document." The suffix on computer filenames indicates the file's encoding convention (file format) rather than actual file content, but some do give you some clue about the type of content. For example, some files created with Microsoft Word end in .dot, indicating the file is a "document template." Moreover, the .doc suffix use only applies to versions of Microsoft Word prior to Office 2007. Word 2007 document files end in .docx, template files end in .dotx, macro-enabled document files end in .docm, and macro-enabled document template files end in .dotm.
Rai Doc ended in 2007.
The three letter extension at the end of every file name is for windows to identify the file format. Some Common file extensions are: .BAT -DOS batch file, .BMP - a bitmap picture image, .DOC -Microsoft Word word processor file format, .EXE -Executable file, .GIF - Graphic Image Format file, .HTM or .HTML, .JPG - Joint Producers and Engineers of Graphics file format, .PDF -Portable Document Format.
Doc Savage Magazine ended in 1949.
That's My Doc ended on 2008-10-04.
Many of them change to -ies for the plural.
Doc - TV series - ended on 2004-11-28.
the games will change
If you mean you've changed the extension on it so it's no longer ".doc" or ".docx" whatever MS uses these days, simply rename it and add the .doc on the end and Microsoft windows should recognize it and open it normally. Failing that, open Word and then select the file anyway manually. The format of the file has not changed, extensions are merely a way for the OS to know what programs correspond to what files or how to use them.
There are two file types in C++ namely, text file and binary file. In text file EOF or end of file is represented by an end of file character having ASCII 26. In binary files EOF or end of file is represented by NULL in the file pointer
That is the file extension. Each file has this extension to tell the system what to do with the file. For example, a program has .exe at the end. This means that it is an executable file, so the system will launch it as a standard executable. A document has .doc or .docx. The system checks file association when you run it, and tells whatever program is set to handle documents to open that file. If you have MS Word, then it will open the file. If you use Open Office, then that program will open it. If you change the extension, then a different program will try to open the file. For example, changing a .jpg to a .txt will open notepad. However, the file is not actually plain text, so you will see many pages of gibberish, since notepad doesn't really know what to do with the image file.