!-----  Ex7_1: Hexadecimal Representation   -----
   PROGRAM Ex7_1
      CHARACTER(LEN=1) :: h(0:15)=(/'0','1','2','3','4','5','6','7' &
                                   ,'8','9','A','B','C','D','E','F'/)
      CHARACTER(LEN=8) :: hex
      INTEGER :: dec
 ext: DO
         hex = " "
         PRINT*, "Input a Positive Integer, or 0 to stop:"
         READ *, dec;  IF( dec <= 0) EXIT ext
 hxd:    DO i = 0, 7
            hex( 8-i : 8-i ) = h( MOD( dec, 16) )
            dec = dec/16;  IF( dec == 0 ) EXIT hxd
         END DO hxd
         PRINT*, hex
      END DO ext
   END PROGRAM Ex7_1