Hi Folks,
Thanks for the help. I'm a TOTAL newbie & using Aitken & Jones "C in 21 days" 870+ pages book to try and understand how it all hangs together in Arduino land.
I suspect MarkT's reply is on the mark. I thought of leading (or trailing) memory locations when looking at the bitwise instructions.
I'm now awaiting the post for my first Uno to arrive . . .
Pat