A little history on the development of computers and the beginnings of modern computers.
Machine d'Anticythère (87 av J.C.)
Calculateur analogique
Elle est considérée comme le premier calculateur analogique antique permettant de calculer des positions astronomiques.
C'est un mécanisme de bronze comprenant des dizaines de roues dentées, solidaires et disposées sur plusieurs plans.
Il est garni de nombreuses inscriptions grecques.
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Le fragment principal de la machine d'Anticythère : 20 à 20 cm environ
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Le boulier
Calculateur manuel
ELes bouliers permettent d'effectuer le calcul des opérations élémentaires : additions, soustractions, multiplications et divisions.
Dans des mains expertes, il est cependant possible de réaliser déautres opérations comme le calcul de racines énièmes ou la conversion entre différentes bases.
Le boulier est lié au système de numération décimale, mais il existe deux grandes catégories de bouliers.
Les bouliers en base 10, pour lesquels chaque boule représente, selon la tige sur laquelle elle se trouve, une unité, une dizaine, une centaineé
Ces bouliers se rencontrent essentiellement en Europe occidentale et de l'Est. Les décimales peuvent aussi être représentées sur la premiére tige.
Et les bouliers en base alternée (5, 2) pour lesquels chaque tige comprend deux parties :
une partie supérieure sur laquelle les boules valent 5 unités (ou 5 dizaines, 5 centaines selon la position de la tige) et une partie inférieure sur
laquelle les boules valent 1 unité (ou 1 dizaine, 1 centaineé selon la position de la tige). Ces bouliers se rencontrent essentiellement en Asie.
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Blaise PASCAL (1623-1662)
Calculating machine conceived in 1642 :
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It possible to add and subtract two numbers in a direct way and make multiplication and division by repetitions.
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A pascaline signed by Pascal in 1652, visible at the Museum of Arts and Crafts in Paris.
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Gottfried Wihelm LEIBNIZ (1646-1716)
Machine presented to the Royal Society of London in 1673 :
Translation of the text of Leibniz Colette Chantal Adam
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Leibniz described herein his arithmetical machine, on which he worked from his youth, and which allows for multiplication by shifting a
movable part of a step to the left, as when asking a multiplication by hand..
Leibniz dreamed of a logic that would algorithmic calculation and therefore mechanically decidable (ratiocinator calculus).
Leibniz and ad artificial and purely formal language developed by Frege.
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Willgodt Theophil ODHNER (1845 - 1905)
Arithmometer of Odhner invented in Russia in 1873 :
Odhner had the idea of ??the machine while repairing a arithmometer 1871 (The Arithmometer was the only mechanical calculator commercialized at the time).
He decided to replace the cylinder Leibniz that made heavy and unwieldy machine, wheels of varying number of teeth, which were lighter and more compact.
Keeping the same procedure, he assured an immediate success.
Odhner finished his first prototype in 1873. In 1876 he built 14 machines Ludvig Nobel, his employer at the time, it will end in 1877.
He filed for patents for invention in Europe and the United States between 1878-1879 and a new patent in 1890. He began his industrial production
in 1890 Arithmometer.
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A luxury mechanical calculator presented to Swedish king Gustaf V by Wilgodt Odhner. TM22900. Photo:Archive of National Museum of Science and Technology.
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Charles BABBAGE (1791-1871)
Difference engine
Babbage began in 1822 with what he called the difference engine, made to compute values of polynomial functions.
It was created to calculate a series of values automatically. By using the method of finite differences, it was possible to avoid the need for multiplication and division.
Some parts of the prototype survive in the Museum of the History of Science, Oxford.[137] This prototype evolved into the "first difference engine." It remained unfinished
and the finished portion is located at the Science Museum in London. This first difference engine would have been composed of around 25,000 parts, weigh fifteen tons (13,600 kg),
and would have been 8 ft (2.4 m) tall.
Analytical engine
The major innovation was that the Analytical Engine was to be programmed using punched cards:
the Engine was intended to use loops of Jacquard's punched cards to control a mechanical calculator, which could use as input the results of preceding computations.
The machine was also intended to employ several features subsequently used in modern computers, including sequential control, branching and looping.
It would have been the first mechanical device to be, in principle, Turing-complete. The Engine was not a single physical machine, but rather a succession of designs
that Babbage tinkered with until his death in 1871.
Babbage had no research team. Ada Lovelace corresponded with him during his development of the Analytical Engine. She is credited with developing an algorithm
for the Analytical Engine to calculate a sequence of Bernoulli numbers. Although there is disagreement over how much of the ideas were Lovelace's own,
she is often described as the first computer programmer.
Completed models
The London Science Museum has constructed two Difference Engines according to Babbage's plans for the Difference Engine No 2. One is owned by the museum.
The other, owned by the technology multimillionaire Nathan Myhrvold, went on exhibition at the Computer History Museum in Mountain View, California on 10 May 2008.
The two models that have been constructed are not replicas; Myhrvold's engine is the first designed by Babbage, and the London Science Museum's is a later model.
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Unfinished prototype (1871) of Babbage's analytical engine, on display in the Science Museum, London.
Part of Charles Babbage's difference engine, assembled after his death by his son, Henry Prevost Babbage (1824-1918), using parts found in Charles' laboratory.
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Alan Turing (1912-1954)
a-machine
" We may compare a man in the process of computing a real number to a machine which is only capable of a finite number of conditions q1: q2. .... qn;
which will be called " m-configurations ". The machine is supplied with a "tape" (the analogue of paper) running through it, and divided into sections
(called "squares") each capable of bearing a "symbol". At any moment there is just one square, say the r-th, bearing the symbol T(r) which is "in the machine".
We may call this square the "scanned square". The symbol on the scanned square may be called the " scanned symbol". The "scanned symbol" is the only one of
which the machine is, so to speak, "directly aware". However, by altering its m-configuration the machine can effectively remember some of the symbols which
it has "seen" (scanned) previously. The possible behaviour of the machine at any moment is determined by the m-configuration qn and the scanned symbol T(r).
This pair qr, T(r) will be called the '' configuration'': thus the configuration determines the possible behaviour of the machine. In some of the configurations
in which the scanned square is blank (i.e. bears no symbol) the machine writes down a new symbol on the scanned square: in other configurations it erases
the scanned symbol. The machine may also change the square which is being scanned, but only by shifting it one place to right or left. In addition to any
of these operations the m-configuration may be changed.... If at each stage the motion of a machine is completely determined by the configuration,
we shall call the machine an "automatic machine" (or a-machine)."
Extract of On computable numbers...[Turing 1936]
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The first a-machine described by Turing in 1936 to compute the sequence "0 1 0 1 0 1 0 1 0 1...".
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Curt Herzstark (1902-1988)
Curt Herzstark was arrested in 1943 by the Nazis and interned in the Buchenwald camp. His technical expertise saves him the worst and he can work on plans for his "Curta" calculator.
The Curta is a small mechanical calculator produced between 1948 and 1972 by Contina AG Mauren in Liechtenstein.
It is composed of a cylindrical body and a small crank making it look like a pepper or coffee grinder.
This very small machine makes it possible to carry out very quickly the four basic arithmetic operations and, after learning, other operations such as square roots.
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Curt Herzstark or La calculatrice Curta on Wikipedia.
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von Neumann (1903-1957)
Architecture de von Neumann
The earliest computing machines had fixed programs. Some very simple computers still use this design, either for simplicity or training purposes. For example, a desk calculator
(in principle) is a fixed program computer. It can do basic mathematics, but it cannot be used as a word processor or a gaming console. Changing the program of a fixed-program machine
requires re-wiring, re-structuring, or re-designing the machine. With the proposal of the stored-program computer this changed. A stored-program computer includes by design an instruction
set and can store in memory a set of instructions (a program) that details the computation.
The term Von Neumann architecture, also known as the Von Neumann model or the Princeton architecture, derives from a 1945 computer architecture description by the
mathematician and physicist John von Neumann and others, First Draft of a Report on the EDVAC.
This describes a design architecture for an electronic digital computer with subdivisions of a processing unit consisting of 4 parts:
- an arithmetic logic unit and processor registers; (UAL) ou unité de traitement, qui effectue les opérations de base;
- a control unit containing an instruction register and program counter;
- a memory to store both data and instructions;
- external mass storage, and input and output mechanisms.
The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and a data operation cannot occur at the same time because they share a common bus
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Von Neumann architecture scheme
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