$LANGUAGE_NUM: Number of current language

$LANGUAGE_NUM expands to an integer that uniquely defines the current language, as follows:

Language	$LANGUAGE_NUM
C	0
C++	1
Fortran	2
Fortran-90	3
Ratfor	4
Ratfor-90	5
TeX	6
VERBATIM	7

This built-in is useful in conjunction with an $IFCASE construction; see $IFCASE.