On Dec 14 2009, Bill Long wrote:

You can write an include file that will compile in either fixed or free source form. The trick is continuation lines, where you put & in column 73 of the first line and & in column 6 of the second. Otherwise, write in fixed form, which is just one particular choice of free form.

Provided that you avoid doing certain things, most of which are perverse, such as putting spaces within keywords or variables. I agree that it's not hard to write readable dual-mode code.

The other topic of this thread has been whether a compiler named 'f77' or some variant thereof will compile a program with f95 features. I can't speak for all vendors, but it would seem like a waste of effort to actually support two separate compilers, one for f77 and one for standard Fortran. ...

As you say, few vendors seem to do it nowadays. It used to be common up to a decade or so ago, but I haven't seen it in some time. Except, of course, under the sort of Linux which has gfortran, g95, f2c, g77, ratfor and any other Fortran-like compiler it can lay its hands on. My impression is that about half the vendors have a command called f77 or similar which is, as you say, the Fortran 90+ compiler with the legacy flags set. The other half don't bother. Most of the users I deal with regard the Fortran compiler command name as an system-specific incantation and wouldn't care much if it were spelled abracadabra, as long as 'man Fortran' told them its name. Regards, Nick Maclaren.