The FORTRAN preprocessor supports the following compiler directives:
$[option]SET (identifierlist)
$[option]IF (conditionlist)
$[option]INCLUDE 'filename'
The $IF directive does not support logical operators. (Note that
the compiler and preprocessor may not support the same things.)
Only simple TRUE and FALSE logical variables are supported. If
the $INCLUDE directive is used and the user include file
contains embedded SQL commands, there cannot be duplicate host
variable type declaration sections. The program unit being
preprocessed and the file that is included cannot both contain
BEGIN DECLARE SECTION and END DECLARE SECTION commands.
However, one or the other may contain a host variable type
declaration section.
The $ must be the first character in the line, and must be
followed by any compiler directives. For the Series 900, refer
to the HP FORTRAN 77/XL Reference Manual for MPE XL on HP
3000 Series 900 Computers (Part Number 31501-90010) for more
information on FORTRAN compiler directives.