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--- talk:analyticalengine:zeroingtemporaries [2015-04-23 04:02] – tim
+++ talk:analyticalengine:zeroingtemporaries [2015-04-23 16:10] (aktuell) – tim
@@ Zeile 34: / Zeile 34: @@
 - Ah, but this is nowhere mentioned in the //Sketch//. A first check gives the indication that this may be possible in the Bernoulli example; have to check it. May collide with loops. Is there a hint anywhere else? Or did I not see it in the //Sketch//? -- Rainer
+Here's the central issue.  The store needs a vast number of parts, so Babbage wanted each column to be as simple as possible.  When a number is given off (read out) there has to be a zero stop, to prevent any possibility that the wheel could overshoot past zero.  That same zero stop would also prevent a wheel passing beyond 9 when moving in the other direction.  In the storage columns in de2 Babbage had to arrange for the zero stop to be lifted out of the way when a number is being added into the column.  So in the AE, an "add without carry" would still require a mechanism to remove the zero stop.  I don't think there was such an arrangement (though there may have been in some particular version), so any attempt to store to a non zero location would result in a jam (or worse physical damage).  == Tim