How to write bytes in a binary file?

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7

I have tested that program on a x86_64 machine:

program writing_bytes
    use ISO_FORTRAN_ENV, only: INT8, INT16
    implicit none
    integer(INT8)  :: i8, j8
    integer(INT16) :: i16
    character(len=1) :: c1
    integer :: status

    ! 129 = 0x81 = 0b10000001
    i8 = int(z'81', kind=INT8)
    print *, i8
    i16 = 129
    j8 = int(i16, kind=INT8)
    print *, j8

    c1 = achar(129)

    open(unit=1, file='bytes.bin', access='stream', status='replace', &
       & action='write', iostat=status)
    write(1, iostat=status) i8, j8, c1
    close(1, iostat=status)

    call execute_command_line("hexdump -C bytes.bin")
end program

This is the output:

$ gfortran writing_bytes.f90 && ./a.out
 -127
 -127
00000000  81 81 81                                          |...|
00000003

It does the job on my machine, both with int( , kind=int8) and achar(). Will it work on any processor?

Note also that if you write i8 = int(129, kind=INT8), gfortran complains:

Error: Arithmetic overflow converting INTEGER(4) to INTEGER(1) at (1). This check can be disabled with the option ‘-fno-range-check’: