c===========================================================
c     Demonstration main program and subroutine
c     to illustrate use of COMMON blocks for creating 
c     'global' storage.  Common blocks should always 
c     be labelled (named) and should be used sparingly.
c===========================================================
      program         tcommon

      implicit        none

c-----------------------------------------------------------
c     Declare variables to be placed in common block 
c-----------------------------------------------------------
      character*16    string
      real*8          v(3),        
     &                x,             y,            z
      integer         i
c-----------------------------------------------------------
c     Variables are stored in a common block in the 
c     order in which they are specified in the 'common'
c     statement. ALWAYS order variables from longest to 
c     shortest to avoid "alignment problems".  Don't 
c     try to put a variable in more than one common block
c     and note that entire arrays (such as 'v') are placed
c     in the common block by simply specifying the name
c     of the array.  Finally, note that variables in a 
c     common block CAN NOT be initialized with a 'data'
c     statement.
c-----------------------------------------------------------
      common   / coma /
     &                string,
     &                v,                                
     &                x,             y,            z,
     &                i

      string = 'foo'
      v(1) = 1.0d0
      v(2) = 2.0d0
      v(3) = 3.0d0
      x = 10.0d0
      y = 20.0d0
      z = 30.0d0
      i = 314

      call subcom()

      stop
      end

c===========================================================
c     This subroutine dumps information passed to it in
c     a common block.
c===========================================================
      subroutine  subcom()
         
c-----------------------------------------------------------
c     Overall layout of common block should be identical 
c     in all program units which use the common block.
c-----------------------------------------------------------
         character*16    string
         real*8          v(3),
     &                   x,             y,            z
         integer         i

         common   / coma /
     &                   string,
     &                   v,
     &                   x,             y,            z,
     &                   i

         write(0,*) 'In subcom:'
         write(0,*) 'string = ', string
         write(0,*) 'v = ', v
         write(0,*) 'x = ', x, ' y = ', y, ' z = ', z
         write(0,*) 'i = ', i

         return

      end