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
Operations.
Third Series, which contains
only one (final) operation.
We do not enter into the same detail of every step of the
processes as in the examples of Notes D. and G., thinking it
unnecessary and tedious to do so. The reader will remember the meaning
and use of the upper and lower indices, &c., as before explained.
To proceed: we know that
Consequently, a slight examination of the second line of (2.) will show
that by making the proper substitutions, (2.) will become
These coefficients should respectively appear on
We shall perceive, if we inspect the particular arrangement of the
results in (2.) on the Result-columns as represented in the diagram,
that, in order to effect this transformation, each successive
coefficient upon , , &c.
(beginning with ), must through means of proper
cards be divided by two[25]; and that one of the halves thus[Pg 49] obtained
must be added to the coefficient on the Variable which precedes
it by ten columns, and the other half to the coefficient on the
Variable which precedes it by twelve columns; ,
, &c. themselves becoming zeros during the process.
This series of operations may be thus expressed:—
Fourth Series.[26]
The calculation of the coefficients , ,
&c. of (1.), would now be completed, and they would stand ranged in
order on , , &c. It will be
remarked, that from the moment the fourth series of operations is
ordered, the Variables , ,
&c. cease to be Result-Variables, and become mere
Working-Variables.
The substitution made by the engine of the processes in the second
side of (3.) for those in the first side, is an excellent illustration
of the manner in which we may arbitrarily order it to substitute any
function, number, or process, at pleasure, for any other function,
number or process, on the occurrence of a specified contingency.
We will now suppose that we desire to go a step further, and to obtain
the numerical value of each complete term of the product (1.),
that is of each coefficient and variable united, which for the
()th term would be .
We must for this purpose place the variables themselves on another
set of columns, , , &c., and
then order their successive multiplication by ,
, &c., each for each. There would thus be a
final series of operations as follows:—
Fifth and Final Series of Operations.
(N.B. that being intended to receive the
coefficient on which has no variable, will
only have inscribed on it, preparatory to
commencing the fifth series of operations.)
From the moment that the fifth and final series of operations is
ordered, the Variables , , &c.
then in their turn cease to be Result-Variables and become mere
[Pg 50]
Working-Variables; , , &c.
being now the recipients of the ultimate results.
Public-domain text, read in full here on John Shaqi.
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