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 being required that the result shall be developed, like the dividend
and the divisor, in successive powers of . A little consideration
of (1.), and of the steps through which algebraical division is
effected, will show that (if the denominator be supposed to consist
of terms) the first partial quotient will be completed by the
following operations:—
that the second partial quotient will be completed by an exactly
similar set of operations, which acts on the remainder obtained by
the first set, instead of on the original dividend. The whole of the
processes therefore that have been gone through, by the time the
second partial quotient has been obtained, will be,—
which is a cycle that includes a cycle, or a cycle of the second order.
The operations for the complete division, supposing we propose
to obtain terms of the series constituting the quotient, will
be,—
It is of course to be remembered that the process of algebraical
division in reality continues ad infinitum, except in the few
exceptional cases which admit of an exact quotient being obtained. The
number in the formula (4.), is always that of the number of terms
we propose to ourselves to obtain; and the th partial quotient is
the coefficient of the ()th power of .
There are some cases which entail cycles of cycles of cycles, to
an indefinite extent. Such cases are usually very complicated, and they
are of extreme interest when considered with reference to the engine.
The algebraical development in a series, of the th function of any
given function, is of this nature. Let it be proposed to obtain the
th function of
We should premise that we suppose the reader to understand what is
meant by an th function. We suppose him likewise to comprehend
distinctly the difference between developing an th
function algebraically, and merely calculating an th
function arithmetically. If he does not, the following will
be by no means very intelligible; but we have not space to give any
preliminary explanations. To proceed: the law, according to which the
successive functions of (5.) are to be developed, must of course first
be fixed on. This law may be of very various kinds. We may propose to
obtain our results in successive powers of , in which case
the general form would be
[Pg 52]
or in successive powers of itself, the index of the function we
are ultimately to obtain, in which case the general form would be
and would only enter in the coefficients. Again, other functions
of or of instead of powers, might be selected. It
might be in addition proposed, that the coefficients themselves should
be arranged according to given functions of a certain quantity. Another
mode would be to make equations arbitrarily amongst the coefficients
only, in which case the several functions, according to either of
which it might be possible to develop the th function of (5.),
would have to be determined from the combined consideration of these
equations and of (5.) itself.
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