Define Big/Little Endian ( was: Re: RISC Mach...)

[M. J. Halloran II McDonnell Douglas M&E]

In article <6200024 at ux1.cso.uiuc.edu>, phil at ux1.cso.uiuc.edu writes:
> Another problem you can encounter when dealing with data structure formats
> imposed by hardware, particularly external hardware, is the byte order.
> An example is handling TCP and IP headers.  The exact data structure is
> defined very specifically, but making code that can deal with it AND be
> portable across big and little endian machines requires a lot of care.
                  ---     ------ ------
		   Let's clerify...
> Such portable code may not be the most optimal depending on how it is
> done.
> 
> --Phil Howard, KA9WGN--
> <phil at ux1.cso.uiuc.edu>

   These define how bytes within words are ordered.

Big endian:    Big end first (MSB)(LSB).
Little endian: Little end first (LSB)(MSB).

	ie: 

	typedef union {
		unsigned char bytes[2];
		unsigned long word;
	    } INDIANS;

	main()	{

	        INDIAN indian;

	    indian.word = 0x1234;

	    if ( indian.bytes[0] == 0x12) /* is MSB at lower mem? */
		puts ( "Big Endian\n");
	    else
		puts ( "Little Endian\n");
	}