subroutine user_card
c
c set up user datacards
c see example below
c 
      implicit none
c
c user datacard values common
c suppose that this common includes a variable mycar_val
c
c     include'user_datacard.inc'
c
c set up datacards
c suppose that you want a datacard mycar associated with the
c value mycar_var
c
c     call ffkey('mycar', mycar_var,  1, 'mixe')
c
      end