Wow! and Wow again. Many many thanks, Willum, for taking so much time and effort in your comprehensive and clear reply. I think I've grasped the essential points but am going away now with a printed copy for further study just to make sure it gets ha
mmered home.
What sparked off my query was in reading the other day that computer chips now contain millions of transistors - the on/off switches - and that shortly even smaller chips will contain even more, i.e talking in terms of billions. I was reminded of a visit to a new computer installed in my place of work in the late fifties and was suitably impressed by the rows of 6 to 7 foot high metal cabinets and the huge reels of magnetic tape whirring back and forth, all of which could now be replaced by the not so humble home PC sitting in front of me. Simply awesome.

Thanks again Bill.

Ogre.

Thinks. This is someone else who must eat as much fish as Alec....