*FLOAT64
      PRINT "Digital root of 627615 is "; FNdigitalroot(627615, 10, p) ;
      PRINT " (additive persistence " ; p ")"
      PRINT "Digital root of 39390 is "; FNdigitalroot(39390, 10, p) ;
      PRINT " (additive persistence " ; p ")"
      PRINT "Digital root of 588225 is "; FNdigitalroot(588225, 10, p) ;
      PRINT " (additive persistence " ; p ")"
      PRINT "Digital root of 393900588225 is "; FNdigitalroot(393900588225, 10, p) ;
      PRINT " (additive persistence " ; p ")"
      PRINT "Digital root of 9992 is "; FNdigitalroot(9992, 10, p) ;
      PRINT " (additive persistence " ; p ")"
      END

      DEF FNdigitalroot(n, b, RETURN c)
      c = 0
      WHILE n >= b
        c += 1
        n = FNdigitsum(n, b)
      ENDWHILE
      = n

      DEF FNdigitsum(n, b)
      LOCAL q, s
      WHILE n <> 0
        q = INT(n / b)
        s += n - q * b
        n = q
      ENDWHILE
      = s