Sketch of the Analytical Engine invented by Charles Babbage, Esq.Menabrea, Luigi Federico
Science
Sketch of the Analytical Engine invented by Charles Babbage, Esq.
Menabrea, Luigi Federico
Babbage, Charles, 1791-1871; Numerical analysis
It will be obvious that the very same seventy-five
Variable-cards may be repeated for the computation of every succeeding
Number, just on the same principle as admits of the repetition of
the thirty-three Variable-cards of Operations (13 ... 23) in the
computation of any one Number. Thus there will be a cycle of
a cycle of Variable-cards.
If we now apply the notation for cycles, as explained in Note E, we may
express the operations for computing the Numbers of Bernoulli in the
following manner:—
Again,
represents the total operations for computing every number in
succession, from to inclusive.
In this formula we see a varying cycle of the first
order, and an ordinary cycle of the second order. The latter
cycle in this case includes in it the varying cycle.
[Pg 65]
On inspecting the ten Working-Variables of the diagram, it will be
perceived, that although the value on any one of them (excepting
, and ) goes through a series of
changes, the office which each performs is in this calculation
fixed and invariable. Thus always
prepares the numerators of the factors of any ;
the denominators. always
receives the ()th factor of , and
the ()th. always decides
which of two courses the succeeding processes are to follow, by feeling
for the value of through means of a subtraction; and so on; but
we shall not enumerate further. It is desirable in all calculations,
so to arrange the processes, that the offices performed by the
Variables may be as uniform and fixed as possible.
Diagram for the computation by the Engine of the Numbers of Bernoulli.
See Note G. (page 67 et seq.)
[Pg 66]
Number of operation.
Nature of operation.
Variables acted upon.
Variables receiving results.
Indication of change in the value of any Variable.
Statement of Results.
Data.
Working variables.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
2
4
0
0
0
0
0
0
0
0
0
0
1
2
1
3
1
4
0
0
5
2
6
0
7
1
8
9
10
11
0
12
13
14
15
16
0
17
18
19
20
0
21
0
22
0
23
Here follows a repetition of Operations thirteen to twenty-three
24
25
by a Variable-card.
0
0
Number of operation.
Result Variables.
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
[Pg 67]
Supposing that it was desired not only to tabulate ,
, &c., but , ,
&c.; we have only then to appoint another series of Variables,
, , &c., for receiving
these latter results as they are successively produced upon
. Or again, we may, instead of this, or in addition
to this second series of results, wish to tabulate the value of each
successive total term of the series (8), viz: ,
, , &c. We have
then merely to multiply each with each corresponding
, as produced; and to place these successive products on
Result-columns appointed for the purpose.
The formula (8.) is interesting in another point of view. It is one
particular case of the general Integral of the following Equation of
Mixed Differences:—
Public-domain text, read in full here on John Shaqi.
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