c  declaration of global variables
        integer  nx
        real     pi
	parameter  (pi = 3.1415927, nx = 21)
c   program (main)
      integer  ntmax,nout,nt
      real     tmax,dt,time,alpha,s,f0
c   grid parameters
      real     xmin,xmax,x(nx),dx
c   fields
      real     f(nx),fold(nx)
c   initial conditions
      real     fini
c   boundary conditions
      real     fb0(2), fb1(2)
c   supplementary fields
      integer  nterm
      real     fexact(nx)
c ------------ : ------------
      common / progr    /  ntmax,nout,nt,tmax,dt,time,alpha,s,f0
      common / gridp    /  xmin,xmax,x,dx
      common / fields   /  f,fold
      common / initc    /  fini
      common / boundc   /  fb0,fb1
      common / supplem  /  nterm,fexact