Back 40 years ago, Data General's AOS/VS defined 255 file types. In many cases, maybe all, there was a corresponding extension for the file, e.g. .exe for execu

Back 40 years ago, Data General's AOS/VS defined 255 file types. In many cases, maybe all, there was a corresponding extension for the file, e.g. .exe for executables, .txt for text and so on. However, there was a trick that I encountered: copies made not by a CLI command or a properly written utility, say by sending a file over email, did not preserve the type in the filesystem. Then you would try to compile or assemble the code somebody sent you, and get a baffling message about your file being of the wrong type. If you had encountered this before, you would REN xyz.asm xyz.xyz CREATE/TYPE=ASM xyz.asm COPY/APPEND xyz.asm xyz.xyz DEL/V xyz.xyz and go on with your work.