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
Thirdly. It may be desired to compute the numerical value of various
subdivisions of each term, and to keep all these results
separate. It may be required, for instance, to compute each coefficient
separately from its variable, in which particular case the engine must
appropriate two result-columns to every term that contains
both a variable and coefficient.
There are many ways in which it may be desired in special cases to
distribute and keep separate the numerical values of different parts of
an algebraical formula; and the power of effecting such distributions
to any extent is essential to the algebraical character of
the Analytical Engine. Many persons who are not conversant with
mathematical studies, imagine that because the business of the engine
is to give its results in numerical notation, the nature
of its processes must consequently be arithmetical and
numerical, rather than algebraical and analytical.
This is an error. The engine can arrange and combine its numerical
quantities exactly as if they were letters or any other
general symbols; and in fact it might bring out its results in
algebraical notation, were provisions made accordingly. It might
develope three sets of results simultaneously, viz. symbolic
results (as already alluded to in Notes A. and B.); numerical
results (its chief and primary object); and algebraical results
in literal notation, This latter however has not been deemed
a necessary or desirable addition to its powers, partly because the
necessary arrangements for effecting it would increase the complexity
and extent of the mechanism to a degree that would not be commensurate
with the advantages, where the main object of the invention is to
translate into numerical language general formulæ of analysis already
known to us, or whose laws of formation are known to us. But it would
be a mistake to suppose that because its results are given
in the notation of a more restricted science, its processes
are therefore restricted to those of that science. The object of the
engine is in fact to give the utmost practical efficiency to the
resources of numerical interpretations of the higher science of
analysis, while it uses the processes and combinations of this latter.
To return to the trigonometrical series. We shall only consider
the four first terms of the factor
(),
since this will be sufficient to show the method. We propose to
obtain separately the numerical value of each coefficient
, , &c. of (1.). The direct
multiplication of the two factors gives
a result which would stand thus on the engine:—
[Pg 48]
()
()
()
The variable belonging to each coefficient is written below it,
as we have done in the diagram, by way of memorandum. The only
further reduction which is at first apparently possible in the
preceding result, would be the addition of to
(in which case should
be effaced from ). The whole operations from the
beginning would then be—
First Series of
Operations.
Second Series of
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