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
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Number of operations.
Nature of operations.
Variables for Results.
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NOTE E.—Page 19.
[Pg 46]
This example has evidently been chosen on account of its brevity and
simplicity, with a view merely to explain the manner in which
the engine would proceed in the case of an analytical calculation
containing variables, rather than to illustrate the extent of its
powers to solve cases of a difficult and complex nature. The equations
of page 14 are in fact a more complicated problem than the present one.
We have not subjoined any diagram of its development for this new
example, as we did for the former one, because this is unnecessary
after the full application already made of those diagrams to the
illustration of M. Menabrea’s excellent tables.
It may be remarked that a slight discrepancy exists between the formulæ
given in the Memoir as the data for calculation, and the
results of the calculation as developed in the last division of
the table which accompanies it. To agree perfectly with this latter,
the data should have been given as
The following is a more complicated example of the manner in which the
engine would compute a trigonometrical function containing variables.
To multiply
Let the resulting products be represented under the general form
This trigonometrical series is not only in itself very appropriate
for illustrating the processes of the engine, but is likewise of much
practical interest from its frequent use in astronomical computations.
Before proceeding further with it, we shall point out that there are
three very distinct classes of ways in which it may be desired to
deduce numerical values from any analytical formula.
First. We may wish to find the collective, numerical value of the
whole formula, without any reference to the quantities of
which that formula is a function, or to the particular mode of their
combination and distribution, of which the formula is the result and
representative. Values of this kind are of a strictly arithmetical
nature in the most limited sense of the term, and retain no trace
whatever of the processes through which they have been deduced. In
fact, any one such numerical value may have been attained from an
infinite variety of data, or of problems. The values for
and in the two equations (see Note D.), come under this class of
numerical results.
Secondly. We may propose to compute the collective numerical value of
each term of a formula, or of a series, and to keep these results
[Pg 47]
separate. The engine must in such a case appropriate as many columns to
results as there are terms to compute.
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