subroutine cfield(r,z,nc,ez,er,bt)
c---------------------------------------------------------------------------
c
      include 'param_sz.h'
      include 'cfldscom.h'
      include 'constcom.h'
      include 'ucom.h'
c
c--------------------------------------------------------------------------
c*
      if(nc.lt.1 .or. nc.gt.numc)then
        write(ndiag,*)' cell id number (',nc,') is out of range'
        call appendparm
        stop ' Abnormal stop cfield '
      endif
      if(iflag(nc).ge.0)call genfld(nc)
  1   dz=hcll(nc)/(numz-1)
      abz=abs(z)
      if(z.lt.0.)then
      s=-1.
      else
      s=1.
      endif
      nz=abz/dz+1
      if(nz.gt.numz-1)then
      nz=numz-1
      dz1=1.
      else
      dz1=abz/dz-nz+1
      endif
      nr=r/dr(nc)+1
      if(nr.gt.numr-1)then
      nr=numr-1
      dr1=1.
      else
      dr1=r/dr(nc)-nr+1
      endif
      c1=(1.-dr1)*(1.-dz1)
      c2=(1.-dr1)*dz1
      c3=dr1*(1.-dz1)
      c4=dr1*dz1
      er=c1*fer(nr,nz,nc)+c2*fer(nr,nz+1,nc)+
     1   c3*fer(nr+1,nz,nc)+c4*fer(nr+1,nz+1,nc)
      er=er*s
      ez=c1*fez(nr,nz,nc)+c2*fez(nr,nz+1,nc)+
     1   c3*fez(nr+1,nz,nc)+c4*fez(nr+1,nz+1,nc)
      bt=c1*fbt(nr,nz,nc)+c2*fbt(nr,nz+1,nc)+
     1   c3*fbt(nr+1,nz,nc)+c4*fbt(nr+1,nz+1,nc)
      return
      end
c++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*