Beginnings of a revolution - The Computing Universe: A Journey through a Revolution - page 14

captured many of the principles to be found in today's computers. In
particular, Babbage's design separated the section of the machine
where the various arithmetical operations were performed from the
area where all the numbers were kept before and after processing.
Babbage named these two areas of his engine using terms borrowed
from the textile industry: the mill for the calculations, which would
now be called the central processing unit or CPU, and the store for
storing the data, which would now be called computer memory. This
separation of concerns was a fundamental feature of von Neumann's
famous report that first laid out the principles of modern computer
organization.
Another key innovation of Babbage's design was that the instruc-
tions for the machine - or program as we would now call them - were
to be supplied on punched cards. Babbage got the idea of using punched
cards to instruct the computer from an automatic loom ( Fig. 1.18 )
invented in France by Joseph-Marie Jacquard ( B.1.5 ). The cards were
strung together to form a kind of tape and then read as they moved
through a mechanical device that could sense the pattern of holes on
the cards. These looms could produce amazingly complex images and
patterns. At his famous evening dinner parties in London, Babbage
used to show off a very intricate silk portrait of Jacquard that had been
produced by a program of about ten thousand cards.
Babbage produced more than six thousand pages of notes on his
design for the Analytical Engine as well as several hundred engineering
drawings and charts indicating precisely how the machine was to oper-
ate. However, he did not publish any scientific papers on the machine
and the public only learned about his new ambitious vision through a
presentation that Babbage gave in 1840 to Italian scientists in Turin.
The report of the meeting was written up by a remarkable young engi-
neer called Luigi Menabrea - who later went on to become a general in
the Italian army and then prime minister of Italy.

Fig. 1.18 A photograph of Jacquard's
Loom showing the punched cards encod-
ing the instructions for producing intri-
cate patterns. The program is a sequence
of cards with holes in carefully specified
positions. The order of the cards and the
positions of these holes determine when
the needles should be lifted or lowered
to produce the desired pattern.

Ada Lovelace

B.1.5 Joseph-Marie Jacquard (1752-
1834) (left) and Philippe de la Salle
(1723-1804) pictured on a mural in
Lyon (Mur des Lyonnais). Philippe de
la Salle was a celebrated designer, who
made his name in the silk industry.
Jacquard's use of punched cards to pro-
vide the instructions for his automated
loom inspired Babbage, who proposed
using punched cards to program his
Analytical Engine.

It is at this point in the story that we meet Augusta Ada, Countess
of Lovelace ( B.1.6 ), the only legitimate daughter of the Romantic poet,
Lord Byron. Lovelace first met Babbage at one of his popular evening
entertainments in 1833 when she was seventeen. Less than two weeks
later, she and her mother were given a personal demonstration of his
small prototype version of his computing engine. Unusually for women
of the time, at the insistence of her father, Ada had had some mathe-
matical training. After this first meeting with Babbage, Ada got mar-
ried and had children but in 1839 she wrote to Babbage asking him
to recommend a mathematics tutor for her. Babbage recommended