anchor.diff:  c
   20    continue
           ierr=1
  +        errstrng="read_bc"
           close(kr)
           return
   c
  
positive.code:         read(kr,"(a80)") dummy
          j=index(dummy,"=")
          if(j.eq.0) then
            ierr=2
            return
          end if
        end do
  
negative.code:         read(kr,*,end=30,err=30) n,(ibond(j,n),j=1,ndof),
       &   (bond(j,n),j=1,ndof)
          if(n.lt.1.or.n.gt.numnp) then
            ierr=104
            errstrng="read_bc"
            return
          end if
          do j=1,ndof
  