CTags (from Darren Hiebert) generates tag files from source code in C,
C++, Eiffel, Fortran, and Java to be used with vi and its derivatives,
Emacs, and several other editors.

ETags (from GNU Emacs sources) generates tag files from source code in
Pascal, Cobol, Ada, Perl, LaTeX, Scheme, Emacs Lisp/Common Lisp,
Postscript, Erlang, Python, Prolog, and most assembler-like syntaxes.