anchor.diff:             call xyz_read(n,c,atag,fn_in)
              ok=n.ne.0
            end if
  -C         do i=1,n
  -C           write(88,*) i,atag(i),(c(k,i),k=1,3)
  -C         end do
  -C         stop
            if(.not.ok) exit
            write(*,*) "number of atoms", n
            oc1=.false.
  
positive.code:          write(*,*) "Maximum Distance:",rmax 
           write(*,*) "Lattice vectors",(latv(i),i=1,3)
           write(*,*) "Number of bins:",nb
         end if
         stop
  c       
         rmax = 4.0
         nb = 100
  
negative.code: c      ---------------------------      
  c      start checks/balances
  c      ---------------------------      
  c      files
         if(nfil.lt.2) then
           message = "please provide input/output files"
           goto 911
         end if
  c      atom tags
         if(atom1_id.eq.0.and.atom1_tag.eq." ") then
           message = "please provide central atom id or tag"
  