Jacquards' Web (13 page)

Above all,
its entire operation would have been controlled by precisely the same kind of cards that Jacquard used for his revolutionary
loom
.

Reliable proof exists of the exact day when Babbage hit upon the idea of making the principle of Jacquard’s loom so fundamental to the operation of the Analytical Engine.

The struggle Babbage had to come to terms with the mag-nitude of his vision of the Analytical Engine can be surmised from the fact that it took him two years from his initial vision of the Analytical Engine to decide precisely what control system he should use. In Volume II of the notebooks that Babbage himself described as his ‘Scribbling Books’—his extensive hand-written journals preserved at the Science Museum in London—there is an entry for
30
June
1836
which contains the brief but momentous comment:

Suggested Jacard’s loom as a substitute for the drums.

This was the first known time he mis-spelt Jacquard’s name. As we have seen, it wasn’t the last.

What exactly does the entry mean?

It reveals that prior to seeing that the Jacquard cards were ideal for operating his Analytical Engine, Babbage had toyed with the idea of programming his new machine by using a revolving drum featuring little raised studs as a mechanical means of inputting data and operating the machine. This type of drum was, of course, the basis for the control system of Jacques de Vaucanson’s loom.

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The notebook entry of
30
June
1836
marks the decisive moment when Babbage abandoned the idea of using the drum in favour of the Jacquard punched-card system. It was as though the evolution of the best method for controlling an automatic silk-weaving loom had been re-enacted in Babbage’s mind. And, just as had happened in the silk-weaving industry itself, the Jacquard cards had won a resounding success over the de Vaucanson revolving studded drum.

Certainly, it made very good sense for Babbage to plump for the Jacquard cards. For one thing, producing punched cards is much easier and far cheaper than manufacturing studded drums.

Yet, more importantly, the Jacquard control system offered the possibility of a potentially
limitless
programming system, whereas a revolving drum will, by definition, start to repeat itself before long. Yet Babbage did plan to use studded drums to control some internal processes of the Analytical Engine.

Babbage was a prolific writer on industry and machinery. It is possible that Babbage had known about the Jacquard loom since his university days, but in any event that it is likely that by
1836

he would have been familiar with the machine and with how it operated. In London’s Spitalfields district a silk-weaving industry had sprung up that offered far from merely token competition to the silk industry in Lyons itself.

Writing in his
1864
autobiography, Babbage makes explicit the enormous influence and importance of the Jacquard loom: It is known as a fact that the Jacquard loom is capable of weaving any design which the imagination of man may conceive. It is also the constant practice for skilled artists to be employed by manufacturers in designing patterns. These patterns are then sent to a peculiar artist, who, by means of a certain machine, punches holes in a set of pasteboard cards in such a manner that when the cards are placed in a Jacquard loom, it will then weave upon its produce the exact pattern designed by the artist.

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The Analytical Engine

Now the manufacturer may use, for the warp and weft of his work, threads which are all of the same colour; let us suppose them to be unbleached or white threads. In this case the cloth will be woven all of one colour; but there will be a damask pattern upon it such as the artist designed.

But the manufacturer might use the same cards, and put into the warp threads of any other colour. Every thread might even be of a different colour, or of a different shade of colour; but in all these case the
form
of the pattern will be exactly the same—the colours only will differ.

The day when Babbage decided to make use of the Jacquard cards in his design for his Analytical Engine is one of the most momentous in our story. It is, literally, the day when the bridge between the weaving industry and the embryonic information technology industry was created. Babbage’s decision was the most explicit confirmation, by the man who is today regarded as the father of the computer, of the argument at the very heart of this book:
that
in essence a computer is merely a special kind of Jacquard loom
.

Babbage recognized that Jacquard’s
automatic
use of the punched card as the means to control the raising and lowering of the warp threads on the loom for weaving brocade was a development of massive importance. After all, Babbage was basically trying to build a computer program a century before the word

‘program’ acquired this meaning, and at a time when ‘computers’

were—as we have seen—people, not machines. He found what he was looking for in Jacquard’s cards. The moment he did, the global information revolution that is such a major part of our lives today took its first substantial step towards incarnation.

Bruce Collier, in his superb study of Babbage’s work,
The
Little Engines that Could’ve
, makes the important comment: The introduction of punched cards into the new engine was important not only as a more convenient form of control than the drums, or because programs could now be of unlimited extent, and could be stored and repeated without the danger 87

Jacquard’s Web

of introducing errors in setting the machine by hand: it was important also because it served to crystallise Babbage’s feelings that he had invented something really new, something much more than a sophisticated calculating machine.

Collier’s point here is of crucial importance. Furthermore,
today
our whole idea of how computers should be programmed and even what
they should actually be can be traced directly back to the Jacquard loom
and its punched cards
. Indeed, the Jacquard card can even be said to constitute the invention of the binary digit or ‘bit’.

A bit in computing terms is the smallest and most fundamental element of computerized information. This basically means that a bit is a unit of information expressed as a choice between two equally probable alternatives. Computers can be built because these alternatives can be boiled down to ‘
0
’ or ‘
1
’, alternatives that can in turn conveniently be represented electronically within the actual physical structure of a computer’s circuitry by a tiny electronic switch that is either ‘off’ (for
0
) or

‘on’ (for
1
).

At the most fundamental level, this is how computers work.

And the whole idea was essentially Jacquard’s.

Writing in his autobiography, Babbage explains how the Analytical Engine would operate. He states that the machine would consist of two parts. These are, firstly, the
store
containing ‘all the variables to be operated upon’, and, secondly, the
mill
‘into which the quantities1 about to be operated upon are always brought’.

Babbage’s use of the terms ‘store’ and ‘mill’ are far-sighted anticipations of the modern computer features of computer memory and computer processor, respectively. In choosing the terms he did, Babbage was also alluding to the cloth industry of Totnes, the town where he spent much of his childhood and to which he often returned as an adult. As the distinguished com-1 In his autobiography Babbage writes ‘qualities’ not ‘quantities’ but this must be a misprint.

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The Analytical Engine

puter historian Martin Campbell-Kelly observes in his introduction to the
1994
reprint of Babbage’s autobiography: This terminology was an elegant metaphor from the textile industry, where yarns were brought from the store to the mill where they were woven into fabric, which was then sent back to the store. In the Analytical Engine, numbers would be brought from the store to the arithmetic mill for processing, and the results of the computation returned to the store.

In his
1864
autobiography, Babbage points out that every formula the Analytical Engine may be required to compute consists of certain algebraic operations to be performed upon given letters, and of certain other operations depending on the numerical value assigned to those letters. By ‘letters’ Babbage is referring to letters in algebraic formulae such as
2x
ϭ
1
;
2y
3 ϭ
16
, etc. although the machine was designed to handle far more complex formulae than this. He adds:

There are therefore two sets of cards, the first to direct the nature of the operations to be performed—these are called operation cards: the other to direct the particular variables on which those cards are required to operate—these latter are called variable cards.

Strictly speaking, Babbage was specifying
three
types of cards, because in practice there were also cards that contained the values to load into the machine. In other words, some cards (the Operation Cards) were to be used to control the actual
operations
of the machine, others (the Variable Cards) to specify
from where
in the store the number to be operated on was to be fetched
, and still others (the Number Cards) were to specify
the actual numbers on
which the machine operates.
A modern computer program works in essentially exactly the same way.

Babbage concludes by making the observation that the Analytical Engine is ‘a machine of the most general nature’. He explains that whatever mathematical formula it is required to 89

Jacquard’s Web

calculate, the details of the formula must be communicated to it by two sets of cards, and that once the machine has been programmed by the cards in this way, the Engine will always operate according to that formula until a new program is fed into it.

Babbage does not himself use the words ‘programming’ or

‘program’. These terms had not yet entered the language and How the Jacquard loom inspired Charles Babbage. These cards, amazing predecessors of the punched cards used to program the computers of the twentieth-century high-tech revolution, were in essence Jacquard cards, but used to weave calculations, not images. They were designed by Babbage.

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The Analytical Engine

he is therefore obliged to resort to more obscure expressions.

For example, he describes the Analytical Engine as being made

‘special’ for the mathematical formula in question. In precisely the same way, we could visualize a Jacquard loom that was programmed to weave a lily as being made ‘special’ for the task of lily-weaving.

Almost as far-sighted as Babbage’s entire concept of the Analytical Engine was his perception of it as having, in effect, a mind of its own. In a fascinating anticipation of the tendency of our own age to invest computers with a will and personality of their own (‘I can’t seem to do this; the computer doesn’t like it’), Babbage consistently writes about the Analytical Engine as if it were a separate, reasoning entity. For example, in the chapter in his autobiography about the Analytical Engine he observes at one point:

Thus the Analytical Engine first computes and punches on cards its own tabular numbers. These are brought to it by its attendant when demanded. But the engine itself takes care that the
right
card is brought to it by verifying the
number
of that card by the number of the card which it demanded. The engine will always reject a wrong card by continually ringing a loud bell and stopping itself until supplied with the precise intellectual food it demands.

Babbage also borrowed from the Jacquard loom the plan of creating what he describes as a ‘library’ of cards that carry out different functions, with the Analytical Engine’s operator being able to take cards from the library as required and input them into the machine in order to make it special for the task. The enormous advantage of the Jacquard loom was, of course, precisely that it was able to weave any picture or pattern for which a chain of cards had been made. Weavers would keep these chains of cards in a storeroom whose function was very much the same as that of the library—or we might even say software library—

which Babbage was proposing to create.

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Babbage planned the Number Cards to express numbers in size up to
10
50–
1
: that is,
9
followed by forty-nine
9
s. In principle each number would be represented by columns, with as many holes punched in each column as were necessary to represent the units, tens, hundreds, thousands, and so on.

Babbage, who always did his utmost to maximize the practical usefulness of the Engines, envisaged a variety of methods in order to simplify how the machine would handle large numbers. These methods involved the Analytical Engine incorporating a variety of card-counting operations, with special holes being used in some cards to indicate that a number exceeded a particular quantity, or that the number itself was negative. The machine was designed to ‘read’ the cards just as the Jacquard loom did. Metal rods in the Analytical Engine mechanism would press against the cards. A particular hole would only register if the rod could poke through it.