THE HISTORY OF THE PASCAL PROGRAMMING LANGUAGE by hcj

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									THE HISTORY OF THE PASCAL PROGRAMMING LANGUAGE Pascal holds a significant spot in the history of computer programming languages. At the time of its invention, it was noted for combining the best features of other available programming languages. Pascal is also known for improving the pointer data type and developing the dynamic variable feature, two important aspects of today‘s programming world.1 Origins Pascal was an offspring of ALGOL, a programming language intended for scientific computing purposes. ALGOL was a platform-independent language, and therefore, the designers had much freedom. This made writing compilers for it more difficult, however.2 The Inventor ―Niklaus Wirth was born in February 1934 in Winterthur, Switzerland. He received the degree of Electronics Engineering from the Swiss Federal Institute of Technology (ETH) in Zurich in 1959, an M.Sc. from Laval University, Canada, in 1960, and a Ph.D. from the University of California at Berkeley in 1963. He was Assistant Professor of Computer Science at Stanford University (1963 - 1967), and then at the University of Zurich. In 1968 he became Professor of Informatics at ETH Zurich. He spent two sabbatical years at the Xerox PARC in California, and he is retired since April 1999‖.3 The Invention Pascal was developed by Niklaus Wirth in the year 1969. He named it after the 17th-century French philosopher and mathematician. The desire of the creator was to have a language that would be sufficient for system design—it would have compilers, operating systems, etc. Wirth also wanted there to be a basis of clear concepts and structures, definable axiomatically and independently of any particular computer. The reason for this feature was he wanted the language to be suitable for the academic environment.4 The language was to rely on systematic thinking, mirror conventional, mathematical notation, satisfy the needs of practical programming, and encourage a structured approach.5 Pascal was successful in these points. Implementations   The first Pascal compiler was developed in 1970. It was for the CDC 6000 computer family. 4 The first successful port of the CDC Pascal compiler to another mainframe was completed by Welsh and Quinn at the Queen's University of Belfast in 1972. The target was the ICL 1900 computer.6

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The History of Computer Programming Languages. November 5, 2004. October 9, 2006. http://www.princeton.edu/~ferguson/adw/programming_languages.shtml
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Learn Pascal. Tao Yue. July 14 2006. October 9, 2006. http://taoyue.com/tutorials/pascal/history.html Department Informatik – Prof. N. Wirth. October 9, 2006. http://www.cs.inf.ethz.ch/~wirth/

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Pascal and its Successors – Niklaus Wirth. September 25, 2002. SwissDelphiCenter.ch. October 9, 2006. http://www.swissdelphicenter.ch/en/niklauswirth.php
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Pascal. June 28, 2001. sd&m. October 9, 2006. http://www.sdm.de/en/it-wissen/themen/sdmkonf-2001/

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Pascal (programming language). October 6, 2006. Wikipedia. October 9, 2006. http://en.wikipedia.org/wiki/Pascal_%28programming_language%29

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The first Pascal compiler written in North America was constructed at the University of Illinois under Donald B. Gillies for the PDP-11 and generated native machine code.1 In order to rapidly propagate the language, a compiler "porting kit" was created in Zurich that included a compiler that generated code for a "virtual" stack machine (i.e. code that lends itself to reasonably efficient interpretation), along with an interpreter for that code - the p-code system. Although the p-code was primarily intended to be compiled into true machine code, at least one system, the notable UCSD implementation, utilized it to create an interpretive system UCSD p-System. The P-system compilers were termed P1-P4, with P1 being the first version, and P4 being the last. 1 Watcom Pascal was developed for the IBM mainframe in the early 1980s. 1 IP Pascal was implemented using Micropolis DOS, but was moved rapidly to CP/M running on the Z80. 1

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In the early 1980s, UCSD Pascal was ported to the Apple II and Apple III computers to provide a structured alternative to the BASIC interpreters that came with the machines. 1 In the 1980s Anders Hejlsberg wrote the Blue Label Pascal compiler for the Nascom-2. A reimplementation of this compiler for the IBM PC was marketed under the names Compas Pascal and PolyPascal before it was acquired by Borland. Renamed to Turbo Pascal it became hugely popular, thanks in part to an aggressive pricing strategy and in part to having one of the first full-screen integrated development environments. 1 The inexpensive Borland compiler greatly influenced the Pascal community that began concentrating mainly on the IBM PC in the late 1980s. Many PC hobbyists in search of a structured replacement for BASIC used this product. It also began adoption by professional developers. 1 Super Pascal existed as a variation of Pascal which added non-numeric labels, a return statement and expressions as names of types. 1 With Turbo Pascal version 5.5 Borland added object orientation to Pascal. Around the same time a number of concepts were imported from C in order to let Pascal programmers use the C-based API of Microsoft Windows directly. These extensions included null-terminated strings, pointer arithmetic, function pointers, an address-of operator and unsafe typecasts. 1 After Turbo Pascal version 5.5, Borland later decided it wanted more elaborate object-oriented features, and started over in Delphi using the Object Pascal draft standard proposed by Apple as a basis. Borland also called this Object Pascal in the first Delphi versions, but changed the name to Delphi Programming Language in later versions. The main additions compared to the older OOP extensions were a referencebased object model, virtual constructors and destructors, and properties. 1 The universities of Zurich, Karlsruhe and Wuppertal developed an EXtension for Scientific Computing (Pascal XSC) based on Oberon, which provides a free solution for programming numerical computations with controlled precision. 1 Rise to Popularity

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The Pascal compiler, UCSD P-System, became a standard when Professor Ken Bowles at the University of California at San Diego adapted the Pascal compiler to the Apple II, the most popular microcomputer of the day. By the early 1980‘s, Pascal had become widely accepted at universities. The Educational Testing Service‘s choice to make Pascal the language upon which the Computer Science Advanced Placement exam for high school students
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Pascal (programming language). October 6, 2006. Wikipedia. October 9, 2006. http://en.wikipedia.org/wiki/Pascal_%28programming_language%29

was based added to Pascal‘s popularity. Pascal was the language of choice for the exam until 1999. The Turbo Pascal compiler for the IBM Personal Computer, designed by Anders Hejlsberg, increased the popularity of Pascal. This compiler‘s prime characteristic was astounding speed. Because of this superiority, Turbo Pascal became the language of choice for programming on the PC. Concurrently, Pascal was chosen as the standard programming language for the then new Apple Macintosh computers.1 Downfall The downfall of the Pascal programming language came with the acceptance of the ‗C‘ programming language. The story goes as such: In the 1970s, Dennis Ritchie and Brian Kernghan of AT&T Bell Laboratories created ‗C.‘ Then, Ritchie and Ken Thompson worked together to create the UNIX operating system. Because of government regulations, AT&T made the decision to give UNIX to universities for free, complete with source code. This led to a whole generation of computer science students learning ‗C‘ in their programming language and operating systems courses. ‗C‘ began to make its way into the programming world. Object-orientation and the PC‘s move to Windows led to the abandonment of Pascal. And, the AP exam moved from Pascal to C++ in 1999.1 The Present There are several reasons while Pascal is mentioned today in the world of computer programming. One reason is the Borland Pascal compiler is still considered to be lightning fast. Borland has produced a Pascal for Windows called Delphi. It is said that, Delphi is to Pascal what Visual BASIC is to BASIC. And, productions are still being made. Pascal is still seen as a good teaching tool when learning the specific details of object-orientation is not necessary. And, despite the intense competition, many small-scale freeware, shareware, and open-source programs written in Pascal/Delphi exist.1

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Learn Pascal. Tao Yue. July 14 2006. October 9, 2006. http://taoyue.com/tutorials/pascal/history.html


								
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