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
In the above case of , the Operation-cards merely order
seven multiplications, that is, they order the mill to be in the
multiplying state seven successive times (without any reference
to the particular columns whose numbers are to be acted upon).
The proper Distributive Variable-cards step in at each successive
multiplication, and cause the distributions requisite for the
particular case.
The engine might be made to calculate all these in succession. Having
completed , the function might be written
under the brackets instead of , and a new calculation
commenced (the appropriate Operation and Variable-cards for the new
function of course coming into play). The results would then appear on
. So on for any number of different functions of the
quantities , , . Each result might either permanently
[Pg 39]
remain on its column during the succeeding calculations, so that when
all the functions had been computed, their values would simultaneously
exist on , , , &c.; or
each result, might (after being jointed off, or used in any specified
manner) be effaced to make way for its successor. The square under
ought, for the latter arrangement, to have the
functions , , , &c. successively
inscribed in it.
Let us now suppose that we have two expressions whose values
have been computed by the engine independently of each other (each
having its own group of columns for data and results). Let them be , . They would then stand as follows on the
columns:—
+
+
+
+
+
+
+
+
+
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
0
0
0
0
0
0
0
0
0
0
We may now desire to combine together these two results, in any
manner we please; in which case it would only be necessary to have
an additional card or cards, which should order the requisite
operations to be performed with the numbers on the two result-columns,
and , and the result of these
further operations to appear on a new column, .
Say that we wish to divide by .
The numerical value of this division would then appear on the
column , beneath which we have inscribed
. The whole series of operations
from the beginning would be as follow ( being = 7):—
This example is introduced merely to show that we may, if we please,
retain separately and permanently any intermediate results (like
), which occur in the course of processes
having an ulterior and more complicated result as their chief and final
object .
Public-domain text, read in full here on John Shaqi.
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