A C89 compiler that produces executables that are also valid ASCII text files [pdf]
There was actually a tool "com2txt" back in the DOS days. So you could convert an executable and put it into an email....<p>Update: I have my data well sorted enough that I found it :-) It even comes with code and is under a vague free license: <a href="https://github.com/hannob/com2txt" rel="nofollow">https://github.com/hannob/com2txt</a>