Ah. Over thirty years ago, I worked with Data General's AOS/VS operating system. I remember very well transferring a source file to another system and finding t

Ah. Over thirty years ago, I worked with Data General's AOS/VS operating system. I remember very well transferring a source file to another system and finding that it would not compile, and gave me an odd message to explain with its refusal. Somehow I learned that the compiler checked to see the type of the file--there were ~255 of them, I think, and on finding that it was FIL and not SRC, rejected it. The cure was to CREATE/type=SRC newfile.c COPY/A newfile.c oldfile.c I know that I was not the last person caught by this, because someone emailed me to say that the source file I had sent him wouldn't compile. (File types and CLI syntax are not guaranteed.)