What programming language was used to write XXX?
Gosling Emacs
Gosling Emacs (often shortened to ``Gosmacs'' or ``gmacs'') is a discontinued Emacs implementation written in 1981 by James Gosling in C. Its extension language, Mocklisp, has a syntax that appears similar to Lisp, but Mocklisp does not have lists or any other structured datatypes.
Mocklisp