As Whiteskin noted, filename extensions are irrelevant in Linux; the execution properties of a file are determined by a combination of its permissions and its magic number (stored within the file itself). So, for example, you could create a shell script and name it readme.txt -- but that wouldn't restrict what you could do with the file. Similarly, if you named the same script readme.exe, the new name would not bestow any new capabilities on the file (i.e., you would not suddenly be able to "execute" the file simply because the name had changed).
Hope this helps.