impl.f

C  Author:   Mitch Richling<http://www.mitchr.me/>
C  IP:       Copyright 1993 by Mitch Richling.  All rights reserved.
C  Key word: FORTRAN f77 do
C  Notes:    Illustrates the IMPLICIT statement -- a rather 
C            dubious feature one often encounters in older
C            code.  In my experience most modern programmers
C            don't use this any more -- in fact, many people
C            use the MIL-STD-1753 extension IMPLICIT NONE to
C            turn this feature off (see implml.f).

C             IMPLicit statement
      program impl

C     The IMPLICIT statement lets one change the default implicit
C     variable types [ IMPLICIT real (a-h), integer (i-n), real (o-z) ].
      implicit double precision (d,x-z), integer (a-c), complex (e,f)

C     You can still override with an explicit declaration:
      integer x

      a = 10.4
      x = 10.3

      write (*,*) 'a=', a
      write (*,*) 'x=', x


      end