How can I change a file type?
A year ago I wrote a few articles that should be viewed in any text type of program. however, I recently opened them and they are viewed in symbols and alphanumeric characters. In linux os, the 'file' is now in an archived folder type that contains .xml files. in windows os it is 'file' as type of file. it has no extension.
Is there any way to recover the original readable alpha-numeric information in these files?
My preference would be to salvage the original information than redo.
First off the extension doesn't actually mean anything for the information of the file, it's only purpose is as a hint to the OS for deciding which application should be used in opening the file. You can prove this by renaming something like an exe to have a txt extension which will then open in notepad as a lot of seemingly random characters; renaming it back to exe will allow it to run again.
Based on your description the files you mention are some form of binary file, the bad news with that is you need to know either what application was used to create the file in order to be able to open it or what the original file extension was (which would be a hint to the former).
If you don't know either of those pieces of information you can of course use trial and error by guessing what extension it might be, renaming it, then opening it with the associated application and seeing if it worked.