Fortran compilers available on SECS Linux/Unix machines as of 15/8/2013

Fortran 77
   f77 invokes /usr/bin/f90 -f77 on lighthouse, i.e. the same as f95
       on lighthouse but with the -f77 option added. 
   g77 is available on barretts

Fortran (all vintages)
   g95 
   gfortran (not on lighthouse or barretts)
   f95 which means different things on different systems. For example, 
      on regent and debretts f95 gets you /usr/pkg/bin/f95 which is
         g95 version 0.93 using gcc version 4.0.3 (Feb 23 2013), but
         /usr/bin/f95 is gfortran using gcc version 4.7.2
      on lighthouse:
         f95 is Sun Fortran 95 8.6 SunOS_sparc Patch 128231-06 2011/11/16 
   ifort is available only via ITS servers such as miro so far as I know.

WARNING: Different compilers implement nonstandard things differently,
e.g. CALL SYSTEM(...) to execute a shell command is OK with gfortran, g95, 
ifort and Sun f95, but gfortran and g95 treat it as an intrinsic subroutine
that's outside the standard, while the others treat it as an external 
subroutine that's always available. So INTRINSIC SYSTEM is allowed among
declarations by gfortran and g95 if you don't also specify -std=f95 or
-std=f2003 to check standard-conformance, while ifort and Sun always object 
to INTRINSIC SYSTEM, but allow CALL SYSTEM(...) whether or not you check 
standard-conformance (-stand f95 or -stand f03 for ifort, -ansi for Sun).

NOTE 1: In spite of the Warning above, there are 4 reasons to try as many 
different compilers as you can with any program. 
(1) Some compilers find bugs that others miss. 
(2) Some compilers give better error messages than others. 
(3) Some programs run much faster with some compilers than others. 
(4) You may get different outputs from the same program with different 
    compilers. That may be because the standard allows it (e.g. * format 
    printing) but it may indicate a bug in your program that's too subtle 
    for compilers to catch. Good luck with hunting for it yourself!

NOTE 2: Almost all standard-conforming f77 programs will compile correctly 
with f95 compilers. The main exception is that if your f77 program uses
a function with the same name as an intrinsic (standard) function that is 
in f95 but not f77, e.g. SUM, then F95 will give you the intrinsic function 
instead of yours unless you specify EXTERNAL SUM in any program using it. 
(The same issue affected f66 programs when compiled with f77. If they used 
a function called LEN you needed EXTERNAL LEN unless you wanted to use the 
f77 standard function.)

NOTE 3: Old f77 compilers allowed many features that were not allowed by
the f77 standard; gfortran has implemented more of those than g95 so is 
more likely to let an old program using such features compile and run.
 
NOTE 4: The PGPLOT graphics routines work with gfortran on x86_64 machines
(e.g. regent) but may not with other compilers or on other kinds of machine.
 
NOTE 5: Nothing above refers to Mac or Windows systems - I don't use them.