! This file:
! http://ftp.aset.psu.edu/pub/ger/fortran/hdk/ReverseEndian.f90
!
! Convert a a file with integers/reals to
! the opposite endian by reversing bytes.

program ReverseEndian
implicit none

integer :: j, k
integer, parameter :: NumberOfRecords=5
integer, parameter :: n=3 ! n = WordsPerRecord.
character (Len=4) :: EndianIn(n), EndianOut(n)
integer, parameter :: RecLen=len(EndianIn)*n  ! in bytes

! Assume records are Binary, so use Direct access.
open (unit=50,file='Data.inp',status='old',             &
       access='direct', form='unformatted', recl=RecLen)
open (unit=60,file='Data.out',                          &
       access='direct', form='unformatted', recl=RecLen)

do k=1,NumberOfRecords
    read(50,rec=k) EndianIn
!   Reverse the bytes (convert Endian byte order)
    FORALL(j = 1:n) EndianOut(j)(4:4)=EndianIn(j)(1:1)
    FORALL(j = 1:n) EndianOut(j)(1:1)=EndianIn(j)(4:4)
    FORALL(j = 1:n) EndianOut(j)(3:3)=EndianIn(j)(2:2)
    FORALL(j = 1:n) EndianOut(j)(2:2)=EndianIn(j)(3:3)
  write(60,rec=k) EndianOut
end do

close(50)
close(60)

end program ReverseEndian