!-----  Ex8_3: Generating a Hexadecimal Representation   -----
   FUNCTION hex(n)
      CHARACTER(LEN=8) :: hex
      CHARACTER(LEN=1) :: h(0:15) = (/ '0', '1', '2', '3', '4', '5', '6', &
                             '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' /)
      INTEGER, INTENT(IN) :: n
      INTEGER ::nin, j, nn
      hex = ' '
      nin = n
      DO j = 8, 1, -1
         nn = nin/16
         hex(j:j) = h(nin-16*nn)
         IF(nn == 0) EXIT     
         nin = nn
      END DO
   END FUNCTION
! --- Main ---
   PROGRAM main
      CHARACTER(LEN=8) :: hex
      INTEGER :: i
      PRINT *, 'Input a positive Integer or negative one to stop:'
      DO
         READ *, i;   IF( i<0 ) EXIT 
         PRINT *, hex(i)
      END DO
   END