March 31, 2018 Saturday
Bedtime Story
Note D of Ada Lovelace - 3 to Note B - 1
We are continuing tonight with Note D of
Ada Lovelace.
“Now the ordinary rule is, that the value
returns to the Variable; unless it has been foreseen that no use for that value
can recurs, in which case zero is substituted.
At the end of a calculation, therefore,
every column ought as a general rule to be zero, excepting those for results.
Thus it will be seen by the diagram, that
when m, the value on V0, is used for the second time by Operation 5,
V0 becomes 0, since m is not needed again; that similarly when (mn’
– m’n), on V12, is used for the third time by Operation 11, V12
becomes zero, since (mn’ – m’n) is not needed again.
In order to provide for the one or the
other of the courses above indicated, there are two varieties of the Supplying
Variable-cards.
One of these varieties has provisions which
cause the number given off from any Variable to return to that Variable after
doing its duty in the mill.
The other variety has provisions which
cause zero to be substituted on the Variable, for the number given off.
The two varieties are distinguished, when
needful, by the respective appellations of the Retaining Supply-cards and the
Zero Supply-cards.
We see that the primary office of both
these varieties of cards is the same; they only differ in their secondary
office.”
Now to understand the concept of office we
will have to leave the Note D for a while and go to Note B.
I know that we are jumping Notes and that ideally
should not be happening, but since here I expect little protest and whatever little
may arise will most likely be ignored in the interest of greater understanding
and flow of the story.
“Note B
This portion of the analytical Engine here
alluded to (by Menabrea) is called the storehouse.
It contains an indefinite number of the
columns of discs described by M. Menabrea.
The reader may picture to himself a pile of
rather large draughtsmen (pieces of draughts game) heaped perpendicularly one
above another to a considerable height, each counter having the digits from 0
to 9 inscribed on its edge at equal intervals; and if he then conceives that
the counters do not actually lie one upon another so as to be in contact, but
are fixed at small intervals of vertical distance on a common axis which passes
perpendicularly through their centers, and around which each disc can revolve
horizontally so that any required digit amongst those inscribed on its margin
can be brought into view, he will have a good idea of one of these columns.
The lowest of the discs on any column
belongs to the units, the next above to the tens, the next above this to the
hundreds, and so on.
Thus if we wished to inscribe 1345 on a
column of the engine, it would stand thus:
1
3
4
5
Stay tuned to the voice of an average story storytelling
chimpanzee or login at http://panarrans.blogspot.com
Good night mon ami and my fellow cousin ape.
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Another great educator and a teacher that I am aware of is
Professor Subhashish Chattopadhyay in Bangalore, India.
While I narrate stories, Professor Subhashish an electronic
engineer and a former professor at BARC, does and teaches real mathematics and
physics.
He started the participation of Indian students at the
International Physics Olympiad.
Do visit him here:
All his books can be downloaded for free through this link:
For edutainment and English education of your children, I
recommend this large collection of Halloween Songs for Kids:
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