c===========================================================
c     fdemo2:  Program which demonstrates basic usage 
c     of character variables in Fortran 77.
c===========================================================
      program         fdemo2

      implicit        none

c-----------------------------------------------------------
c     See below for definition of integer function
c     'indlnb'.   Note that this and other useful routines
c     are available in the 'p410f' library.
c-----------------------------------------------------------
      integer         indlnb

c-----------------------------------------------------------
c     Define some character variables of various lengths
c
c     Note that 
c
c        character*1     foo
c
c     and 
c
c        character       foo
c
c     are synonymous, i.e. if an explicit length 
c     specification is not given, the variable will
c     be a single character long.
c-----------------------------------------------------------
      character*1     c1
      character*2     c2
      character*4     c4
      character*26    lcalph
      character       cc1*1,    cc2*2,   cc4*4
      character*60    buffer

c-----------------------------------------------------------
c     Assignment of constant strings to char. variables.
c     If length of character expression being assigned 
c     is less than length of character variable, variable 
c     is 'right-padded' with blanks.
c-----------------------------------------------------------
      c1     = 'a'
      c2     = 'bc'
      c4     = 'defg'
      lcalph = 'abcdefghijklmnopqrstuvwxyz'
 
      write(*,*) 'c1 = ', c1
      write(*,*) 'c2 = ', c2
      write(*,*) 'c4 = ', c4
      write(*,*) 'lcalph = ', lcalph
      call prompt('Through constant assignment')

c-----------------------------------------------------------
c     // is the string concatentation operator 
c-----------------------------------------------------------
      write(*,*) 'c1 // c2 // c4 = ', c1 // c2 // c4
      call prompt('Through concatenation')

c-----------------------------------------------------------
c     The integer intrinsic (built-in) function 'len'
c     returns the length of its string argument
c-----------------------------------------------------------
      write(*,*) 'len(c1) = ', len(c1)
      write(*,*) 'len(buffer) = ', len(buffer)
      call prompt('Through string length')

c-----------------------------------------------------------
c     Substring extraction
c-----------------------------------------------------------
      write(*,*) 'lcalph(1:13) = ',  lcalph(1:13)
      write(*,*) 'lcalph(18:18) = ', lcalph(18:18)
      call prompt('Through substring extraction')

c-----------------------------------------------------------
c     Substring assignment
c-----------------------------------------------------------
      c4(4:4) = 'Z'
      write(*,*) 'c4 = ', c4
      call prompt('Through substring assignment')

c-----------------------------------------------------------
c     Use of 'indlnb' 
c-----------------------------------------------------------
      buffer = 'somefilename' 
      write(*,*) '<' // buffer // '>'
      write(*,*) '<' // buffer(1:indlnb(buffer)) // '>'
      buffer = 'Some multi-word message' 
      write(*,*) '<' // buffer // '>'
      write(*,*) '<' // buffer(1:indlnb(buffer)) // '>'
      buffer = ' '
      write(*,*) 'indlnb(buffer) = ', indlnb(buffer)
      call prompt('Through indlnb usage')

      call prompt('Through fdemo2')

      stop
      end

c-----------------------------------------------------------
c     Prints a message on stdout and then waits for input 
c     from stdin.
c-----------------------------------------------------------
      subroutine prompt(pstring)

         implicit      none

         character*(*) pstring
         integer       rc
         character*1   resp

         write(*,*) pstring
         write(*,*) 'Enter any non-blank character & '//
     &              'enter to continue'
         read(*,*,iostat=rc,end=900)  resp
         return
 
 900     continue
         stop
      end 

c-----------------------------------------------------------
c     Returns index of last non-blank character in 's',
c     or 0 if the string is completely blank. 
c-----------------------------------------------------------
      integer function indlnb(s)
 
         character*(*)    s
 
         do indlnb = len(s) , 1 , -1
            if( s(indlnb:indlnb) .ne. ' ' ) return
         end do
         indlnb = 0
 
         return
 
      end