*
*******************************************************************************
*
*    This program illustrates the use of the REENTRANT control to write
*    a recursive procedure in FORTRAN-86.  It solves the "towers of Hanoi"
*    problem, which is described as follows:
*
*    There are three pegs, labelled "A", "B", and "C".  Peg A has a stack of
*    disks (number provided by the operator) on it; Pegs B and C have none.
*    Each disk is of a different size, and they are ordered on Peg A by size,
*    starting with the largest on the bottom.  The disks can be moved one at
*    a time to any other peg as long as no disk is placed on top of another
*    disk which is smaller in size.
*
*    How can these disks be transferred from Peg A to Peg B?
*
*
*    NOTE: Due to the recursive nature of this procedure, it may be necessary
*          to increase the 8086 stack size for large numbers of disks.  See 
*          the iAPX 86,88 Family Utilities User's Guide for more information.
*
*******************************************************************************
*

        PROGRAM PROG4

	WRITE(6,100)
100	FORMAT('How many disks are to be moved from peg A to peg B: ',$)
	READ(5,200)NUM
200	FORMAT(I5)

	CALL HANOI('A','B','C',NUM)

	END


$REENTRANT

	SUBROUTINE HANOI(FROM,TO,BUFF,NUM)
	CHARACTER*1 FROM,TO,BUFF

	IF(NUM .EQ. 0) RETURN

	CALL HANOI(FROM,BUFF,TO,NUM-1)

	WRITE(6,100)FROM,TO
100	FORMAT('Move a disk from peg ',A,' to peg ',A)

	CALL HANOI(BUFF,TO,FROM,NUM-1)

	END