c===========================================================
c     Demonstration main program and subroutine to 
c     illustrate use of SAVE and DATA statements.
c===========================================================
      program         tsavedata

      implicit        none

      integer         i

      do i = 1 , 10
         call sub1()
      end do

      stop

      end

c===========================================================
c     Subprogram 'sub1': writes a message to standard 
c     error the FIRST time it is called, and writes 
c     the number of times it has been called so far to
c     standard output EVERY time it is called. 
c===========================================================
      subroutine sub1()
      
         implicit     none

         logical      first 
         integer      ncall
c-----------------------------------------------------------
c        Strict f77 statement ordering demands that 
c        ANY DATA statements appear after ALL variable 
c        declarations.  Note the use of '/' to delimit the 
c        initialization value.
c-----------------------------------------------------------
         data         first / .true. /
c-----------------------------------------------------------
c        This 'save' statement guarantees that ALL local 
c        storage is preserved between calls.   
c-----------------------------------------------------------
         save

         if( first ) then
            ncall = 1
            write(0,*) 'First call to sub1'
            first = .false.
         end if

         write(*,*) 'sub1: Call ', ncall
         ncall = ncall + 1

         return

      end