The Pascal Programming Language

The Pascal language was named for Blaise Pascal, a French mathematician who was a pioneer in computer development history. In 1641, at the age of eighteen, Pascal constructed the first arithmetical machine, arguably the first computer. He would improve upon the instrument eight years later. In 1650, Pascal left the world of geometry and physics, and shifted his focus towards religious studies, or, as Pascal wrote, to "contemplate the greatness and the misery of man." Pascal died in Paris on August 19, 1662.

The earliest computers were programmed in machine code and assembly. This type of programming is tedious and error prone, as well as extremely difficult to understand and modify. Programming is a time-consuming and expensive process. High level languages were developed to resolve this problem. High level languages provide a set of instructions that read like English, but can be translated by a program called a compiler into machine code. Pascal is one such language.

Other high level languages developed in the early years of the computer were FORTRAN (1957), COBOL (1959), ALGOL (1960), APL (1962), BASIC (1964), C (1972) and Ada (1983), to name a few. One problem with many of the early languages (e.g., FORTRAN and BASIC) was the heavy dependency on the use of "goto" instructions. "Goto" instructions tell the computer to jump from one step to another, enabling the computer to skip steps or to go back to repeat earlier steps. This type of sporadic branching increases the difficulty of debugging code. Additionally, languages like COBOL were designed with over-elaborate definitions, weak data structures support, and a lack of flexibility, making programs tedious to code and difficult to enhance.

Niklaus Wirth completed development of the original Pascal programming language in 1970. He based it upon the block structured style of the Algol programming language. There were two original goals for Pascal. According to the Pascal Standard (ISO 7185), these goals were to a) make available a language suitable for teaching programming as a systematic discipline based on fundamental concepts clearly and naturally reflected by the language, and b) to define a language whose implementations could be both reliable and efficient on then-available computers.

Pascal went far beyond its original design goals, with commercial use of the language often exceeding academic interest. Pascal provides rich data structures, including both the enumerated and record data types, and defined with a pleasing and powerful clarity. It provided an orthogonal and recursive approach to data structures, with arrays of arrays, arrays of records, records containing arrays, files of records, files of arrays, files of records containing arrays of records, and so on. Pascal's popularity exploded in the 1970's, as it was used in writing both system and application software. For this reason, the International Standards committee decided that a formal standard was needed to promote the stability of the Pascal language (the ISO 7185 Pascal Standard was originally published in 1983). By the end of the 1970's, more than 80 computer systems had Pascal implementations in use.

One of the more popular Pascal's of the 1970's and early 1980's was UCSD Pascal on the UCSD P-System operating system. The UCSD P-System was developed at the Institute for Information Studies at the University of California - San Diego, under the direction of Kenneth Bowles. In fact, the P-System operating system itself was written in UCSD Pascal. As Wirth writes in his 1985 Turing Award Lecture, From Programming Language Design To Computer Construction, "But Pascal gained truly widespread recognition only after Ken Bowles in San Diego recognized that the P-system could well be implemented on the novel microcomputers. His efforts to develop a suitable environment with integrated compiler, filer, editor, and debugger caused a breakthrough: Pascal became available to thousands of new computer users who were not burdened with acquired habits or stifled by the urge to stay compatible with software of the past."

In 1978, Richard Gleaves and Mark Allen, working on-campus in San Diego, used UCSD Pascal to develop the 6502 interpreter which became the basis for Apple Pascal. By the 1980's, Pascal was used by most universities to teach programming, while still invading the commercial markets. It became so popular that even FORTRAN began to change, taking advantage of Pascal's innovations.

Due to the strong popularity of the Pascal language in system and application software development, and in response to the many cited drawbacks of the original Pascal implementation, an Extended Pascal evolved to address the needs of commercial development. In 1990, the ISO 10206 Extended Pascal Standard was published to support this new version of the language.

In addition to Extended Pascal, in 1986, Apple Computer released the first Object Pascal implementation, a version of its Apple Pascal that supported object-oriented programming. In 1993, the Pascal Standards Committee published an Object-Oriented Extensions to Pascal technical report which was based upon Apple's Object Pascal implementation.

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