Also here a statement function could be used, but is was not popular at that time, and
therefore an external function was being used instead. The backward loop no longer has
to be simulated and the conditional statement can be given in a more natural way.
Structured layout is now the normal case.
The character string can be given within apostrophes so that you no longer have to
count manually the number of characters in the character string. The statement END in
the main program replaces the statement STOP.
Also the explicit RETURN in the function FUN is now optional.