anchor.diff:        if (dimen.eq.0) then
             write(*,*) '!! Error: Problem dimension unspecified'
             call usage('!! Use -2 for 2D, -3 for 3D')
  +      endif
  +C Output file
  +      if (ofile.eq.'none') then
  +          write(*,*) '!! Error: Output file not specified'
  +          call usage('!! Use -o OFILE to define output file')
         endif
   
   C----
  
positive.code: 
  C----------------------------------------------------------------------C
  
        SUBROUTINE gcmdln(fltf,obsf,smooth,smoof,damp,dimen)
        IMPLICIT NONE
        CHARACTER*80 fltf,obsf,tag,smoof
        INTEGER i,narg
        REAL*8 smooth,damp
        INTEGER dimen
        fltf = 'none'
        obsf = 'none'
        smoof = 'none'
        dimen = 0
        smooth = -1.0d0
        damp = -1.0d0
        narg = iargc()
        if (narg.eq.0) call usage('!! Error: no command line arguments')
        i = 0
  
negative.code:       PROGRAM MAIN
        IMPLICIT none
        CHARACTER*80 fltf,obsf,smoof,ofile
        INTEGER dimen,ios,geo
        LOGICAL ex
        REAL*8 smooth,damp
        INTEGER OBSMAX,PARMAX
  