      logical function isnum (a1)                                       ISNU0001
c ----------------------------------------------------------------------ISNU0002
c                                                                       ISNU0003
c     true if a1 is a number (0..9) else false - B.Rupp                 ISNU0004
c                                                                       ISNU0005
c ----------------------------------------------------------------------ISNU0006
WINNT - used by TPLOT, PPLOT                                            ISNU0007
                                                                        ISNU0008
      character a1                                                      ISNU0009
                                                                        ISNU0010
      if ((ichar(a1).gt.47).and.(ichar(a1).lt.58)) then                 ISNU0011
         isnum=.true.                                                   ISNU0012
      else                                                              ISNU0013
         isnum=.false.                                                  ISNU0014
      end if                                                            ISNU0015
      return                                                            ISNU0016
      end                                                               ISNU0017
