!DECK I1MACH
      INTEGER FUNCTION I1MACH (I)
      IMPLICIT NONE
      INTEGER :: I
      REAL :: X
      DOUBLE PRECISION :: XX
!***BEGIN PROLOGUE  I1MACH
!***PURPOSE  Return integer machine dependent constants.
!***LIBRARY   SLATEC
!***CATEGORY  R1
!***TYPE      INTEGER (I1MACH-I)
!***KEYWORDS  MACHINE CONSTANTS
!***AUTHOR  Fox, P. A., (Bell Labs)
!           Hall, A. D., (Bell Labs)
!           Schryer, N. L., (Bell Labs)
!***DESCRIPTION
!
!   I1MACH can be used to obtain machine-dependent parameters for the
!   local machine environment.  It is a function subprogram with one
!   (input) argument and can be referenced as follows:
!
!        K = I1MACH(I)
!
!   where I=1,...,16.  The (output) value of K above is determined by
!   the (input) value of I.  The results for various values of I are
!   discussed below.
!
!   I/O unit numbers:
!     I1MACH( 1) = the standard input unit.
!     I1MACH( 2) = the standard output unit.
!     I1MACH( 3) = the standard punch unit.
!     I1MACH( 4) = the standard error message unit.
!
!   Words:
!     I1MACH( 5) = the number of bits per integer storage unit.
!     I1MACH( 6) = the number of characters per integer storage unit.
!
!   Integers:
!     assume integers are represented in the S-digit, base-A form
!
!                sign ( X(S-1)*A**(S-1) + ... + X(1)*A + X(0) )
!
!                where 0 .LE. X(I) .LT. A for I=0,...,S-1.
!     I1MACH( 7) = A, the base.
!     I1MACH( 8) = S, the number of base-A digits.
!     I1MACH( 9) = A**S - 1, the largest magnitude.
!
!   Floating-Point Numbers:
!     Assume floating-point numbers are represented in the T-digit,
!     base-B form
!                sign (B**E)*( (X(1)/B) + ... + (X(T)/B**T) )
!
!                where 0 .LE. X(I) .LT. B for I=1,...,T,
!                0 .LT. X(1), and EMIN .LE. E .LE. EMAX.
!     I1MACH(10) = B, the base.
!
!   Single-Precision:
!     I1MACH(11) = T, the number of base-B digits.
!     I1MACH(12) = EMIN, the smallest exponent E.
!     I1MACH(13) = EMAX, the largest exponent E.
!
!   Double-Precision:
!     I1MACH(14) = T, the number of base-B digits.
!     I1MACH(15) = EMIN, the smallest exponent E.
!     I1MACH(16) = EMAX, the largest exponent E.
!
!   To alter this function for a particular environment, the desired
!   set of DATA statements should be activated by removing the C from
!   column 1.  Also, the values of I1MACH(1) - I1MACH(4) should be
!   checked for consistency with the local operating system.
!
!***REFERENCES  P. A. Fox, A. D. Hall and N. L. Schryer, Framework for
!                 a portable library, ACM Transactions on Mathematical
!                 Software 4, 2 (June 1978), pp. 177-188.
!***ROUTINES CALLED  (NONE)
!***REVISION HISTORY  (YYMMDD)
!   750101  DATE WRITTEN
!   960411  Modified for Fortran 90 (BE after suggestions by EHG).   
!   980727  Modified value of I1MACH(6) (BE after suggestion by EHG).   
!***END PROLOGUE  I1MACH
!
      X  = 1.0      
      XX = 1.0D0

      SELECT CASE (I)
        CASE (1)
          I1MACH = 5 ! Input unit
        CASE (2)
          I1MACH = 6 ! Output unit
        CASE (3)
          I1MACH = 0 ! Punch unit is no longer used
        CASE (4)
          I1MACH = 0 ! Error message unit
        CASE (5)
          I1MACH = BIT_SIZE(I)
        CASE (6)
          I1MACH = 4            ! Characters per integer is hopefully no
                                ! longer used. 
                                ! If it is used it has to be set manually.
                                ! The value 4 is correct on IEEE-machines.
        CASE (7)
          I1MACH = RADIX(1)
        CASE (8)
          I1MACH = BIT_SIZE(I) - 1
        CASE (9)
          I1MACH = HUGE(1)
        CASE (10)
          I1MACH = RADIX(X)
        CASE (11)
          I1MACH = DIGITS(X)
        CASE (12)
          I1MACH = MINEXPONENT(X)
        CASE (13)
          I1MACH = MAXEXPONENT(X)
        CASE (14)
          I1MACH = DIGITS(XX)
        CASE (15)
          I1MACH = MINEXPONENT(XX)
        CASE (16)
          I1MACH = MAXEXPONENT(XX) 
        CASE DEFAULT
          WRITE (*, FMT = 9000)
 9000     FORMAT ('1ERROR    1 IN I1MACH - I OUT OF BOUNDS')
          STOP
        END SELECT
      RETURN
      END