Difference between revisions of "Basic Pascal Tutorial/History/fr"

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===UCSD Pascal===
 
===UCSD Pascal===
One of the things that killed ALGOL was the difficulty of creating a compiler for it. Dr. Wirth avoided this by having his Pascal compiler compile to an intermediate, platform-independent object code stage. Another program turned this intermediate code into executable code.
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La difficulté de créer un compilateur pour ALGOL a été l'une des choses qui l'a tué. Le Dr Wirth a évité cela en faisant que son compilateur Pascal compile le code objet intermédiaire, indépendant de la plate-forme dans une première étape. Un autre programme transformait le code itermédiaire en code exécutable.
  
Prof. Ken Bowles at the University of California at San Diego (UCSD) seized on the opportunity this offered to adapt the Pascal compiler to the Apple II, the most popular microcomputer of the day. UCSD P-System became a standard, and was widely used at universities. This was aided by the low cost of Apple II's compared to mainframes, which were necessary at the time to run other languages such as FORTRAN. Its impact on computing can be seen in IBM's advertisements for its revolutionary Personal Computer, which boasted that the PC supported three operating systems: Digital Research's CP/M-86, Softech's UCSD P-system, and MicroSoft's PC-DOS.
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Pr. Ken Bowles de l'Université de Californie de San Diego (UCSD) saisit l'opportunité ainsi offerte pour adapter le compilateur sur Apple II, le micro-ordinateur le plus populaire du moment. UCSD P-System devint un standard et fut largement utilisé dans les universités, aidé en cela par le faible prix de l'Apple II comparé à celui d'un mainframe qui était nécessaire en ce temps pour faire tourner des langages comme FORTRAN. Son impact sur ​​l'informatique peut être vu dans les annonces d'IBM pour son révolutionnaire ordinateur personnel, qui vantait que le PC prenait en charge trois systèmes d'exploitation: le CP/M-86 de Digital Research, le UCSD P-system de Softech et le PC-DOS de MicroSoft.
  
 
===Pascal Becomes Standard===
 
===Pascal Becomes Standard===

Revision as of 14:09, 16 March 2014

Template:Object Pascal History

Histoire du Pascal

Origines

Pascal dérive d'ALGOL, un langage de programmation prévu pour le calcul scientifique. Réunis à Zurich, un comité international conçut ALGOL comme langage indépendant de la plate-forme. Cela leur a donné une relative carte blanche dans les fonctions qu'ils pourraient concevoir en ALGOL, mais aussi rendu plus difficile d'écrire des compilateurs pour lui. C'étaient ces jours où manquaient des caractéristiques matérielles que nous prenons maintenant pour acquises. L'absence de compilateurs sur plusieurs plates-formes, combiné avec le manque de pointeurs et de types de données basiques tels que les caractères, ont fait qu'ALGOL n'a pas été largement accepté. Les scientifiques et les ingénieurs ont afflué vers FORTRAN, un langage de programmation qui était disponible sur de nombreuses plates-formes. ALGOL a périclité sauf comme langage de description d'algorithme.

Wirth invente le Pascal

Dans les années 60, pusieurs informaticiens travaillent à étendre ALGOL. L'un d'entre eux est Niklaus Wirth de l'Institut Fédéral de Technologie Suisse (ETH-Zurich), un membre du groupe à l'origine d'ALGOL. En 1971, il publia sa spécification d'un langage hautement structuré de qui ressemblait à ALGOL de plusieurs façons. Il nomma le langage Pascal d'après el philosophe et mathématicien Français du 17ème siècle qui construisit la première machine à calculer.

Pascal est très orienté donnée, donnant au porgrammeur la possibilité de définir des type des données personnalisés. Avec cette liberté vient aussi le contrôle le strict contrôle de type, qui évite de mélanger les types de données. Pascal fut prévu pour comme langage d'apprentissage et a été largement adopté comme tel. Il se lit facilement comme un langage naturel, rendant facile comprendre le code écrit avec.

UCSD Pascal

La difficulté de créer un compilateur pour ALGOL a été l'une des choses qui l'a tué. Le Dr Wirth a évité cela en faisant que son compilateur Pascal compile le code objet intermédiaire, indépendant de la plate-forme dans une première étape. Un autre programme transformait le code itermédiaire en code exécutable.

Pr. Ken Bowles de l'Université de Californie de San Diego (UCSD) saisit l'opportunité ainsi offerte pour adapter le compilateur sur Apple II, le micro-ordinateur le plus populaire du moment. UCSD P-System devint un standard et fut largement utilisé dans les universités, aidé en cela par le faible prix de l'Apple II comparé à celui d'un mainframe qui était nécessaire en ce temps pour faire tourner des langages comme FORTRAN. Son impact sur ​​l'informatique peut être vu dans les annonces d'IBM pour son révolutionnaire ordinateur personnel, qui vantait que le PC prenait en charge trois systèmes d'exploitation: le CP/M-86 de Digital Research, le UCSD P-system de Softech et le PC-DOS de MicroSoft.

Pascal Becomes Standard

By the early 1980's, Pascal had already become widely accepted at universities. Two events conspired to make it even more popular.

First, the Educational Testing Service, the company which writes and administers the principal college entrance exam in the United States, decided to add a Computer Science exam to its Advanced Placement exams for high school students. For this exam, it chose the Pascal language. Because of this, secondary-school students as well as college students began to learn Pascal. Pascal remained the official language of the AP exams until 1999, when it was replaced by C++, which was quickly replaced by Java.

Second, a small company named Borland International released the Turbo Pascal compiler for the IBM Personal Computer. The compiler was designed by Anders Hejlsberg, who would later head the group at Microsoft that developed C# and (re)introduced Managed Code back to the world of computing.

Turbo Pascal was truly revolutionary. It did take some shortcuts and made some modifications to standard Pascal, but these were minor and helped it achieve its greatest advantage: speed. Turbo Pascal compiled at a dizzying rate: several thousand lines a minute. At the time, the available compilers for the PC platform were slow and bloated. When Turbo Pascal came out, it was a breath of fresh air. Soon, Turbo Pascal became the de facto standard for programming on the PC. When PC Magazine published source code for utility programs, it was usually in either assembly or Turbo Pascal.

At the same time, Apple came out with its Macintosh series of computers. As Pascal was the preeminent structured programming language of the day, Apple chose Pascal as the standard programming language for the Mac. When programmers received the API and example code for Mac programming, it was all in Pascal.

Extensions

From version 1.0 to 7.0 of Turbo Pascal, Borland continued to expand the language. One of the criticisms of the original version of Pascal was its lack of separate compilation for modules. Dr. Wirth even created a new programming language, Modula-2, to address that problem. Borland added modules to Pascal with its units feature.

By version 7.0, many advanced features had been added. One of these was DPMI (DOS Protected Mode Interface), a way to run DOS programs in protected mode, gaining extra speed and breaking free of the 640K barrier for accessing memory under DOS. Turbo Vision, a text-based windowing system, allowed programmers to create great-looking interfaces in practically no time at all. Pascal even became object-oriented, as version 5.5 adopted the Apple Object Pascal extensions. When Windows 3.0 came out, Borland created Turbo Pascal for Windows, bringing the speed and ease of Pascal to the graphical user interface. It seemed that Pascal's future was secure.

The World Changes

However, this was not to be. In the 1970s, Dennis Ritchie and Brian Kernighan of AT&T Bell Laboratories created the C Programming Language. Ritchie then collaborated with Ken Thompson to design the UNIX operating system. At the time, AT&T had a government-sanctioned monopoly on telephone service in the United States. In return for the monopoly, its telephone business was regulated and it was prohibited from entering the computer business. AT&T, seeing no market for a research operating system, gave UNIX away to universities for free, complete with source code. Thus, a whole generation of computer science students learned C in their university courses on languages and operating systems. Slowly but surely, C began to filter into the computer programming world.

Pascal was took a heavy hit in the 90s when several large companies focused on other programming languages. Microsoft for example focused on Visual Basic and C, and Apple migrated it's APIs from Pascal to C and later to Objective C. Despite the lack of support from operating system producers, Pascal still retained a large following through Delphi and Free Pascal.

So what are the advantages of learning Pascal?

Despite having lost its previous position of dominance, Pascal is still quite useful, one of its advantages being that it has a very clear syntax which uses common words, such as begin/end, to express concepts, making its code easier to read and maintain.

Another reason: speed and size. Pascal compilers are lightning-fast and Delphi and Free Pascal are no exceptions. While C programmers might wait for hours, Pascal programmers have to wait only 1 minute for a program of a similar size. Besides that the Pascal IDEs are still leaders in terms of productivity in the world through the Delphi IDE and the Lazarus IDE.

Also, Pascal remains preferred at many universities. In addition, Pascal was well-suited for teaching programming, and remains so. There is less overhead and fewer ways for a student to get a program into trouble. For teaching simple procedural programming, Pascal remains a good choice. Pascal has hung on longer in education outside the United States, and remains an official language of the International Informatics Olympiad. A basic programming background is useful in many technical occupations and Pascal is easier to learn than C/C++.

Today Pascal retains a niche in the market through Delphi, Free Pascal and Lazarus. Many small-scale freeware, shareware, open-source and commercial programs are written in Pascal/Delphi. So enjoy learning it. It's a great introduction to computer programming. It's not dangerous like C, confusing like C++, or slow like Java.

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