The Pascal Programming Language

The Pascal language offers a very good approach to programming. Very used in the school environment, it allows to acquire solid notions found in all other languages. The CyberZoïde is one of the very few websites to offer a real programming course in Pascal with many examples and programs annotated for free download.

The basic elements of programming such as: pointers, types, tables, procedures, functions, graphics ... and many others are explained to you with maximum relevance, simplicity and efficiency.

Table of contents

• Introduction
• History, purpose and use
• Pascal vs. C
• Differences
• Parameters
• Statement syntax
• Operators
• Comments
• Case sensitivity
• If-statement
• Strings,
• Similarities
• Blocks
• Variable definitions
• In-line assembly
• Trade-offs
• Ambiguity vs. cluttered grammar
• Case #1: Precedence
• Case #2: Associativity
• Case #3: Dangling else
• Conclusion
• Early vs. late binding
• Strong vs. weak typing
• Static vs. dynamic typing
• Garbage collection or not
• Single vs. multiple inheritance
• Polymorphism
• Procedure/function name overloading
• Operator overloading
• Coercion
• Appendix A: a sample program
• Circle
• Overloading
• Appendix B: information sources

History of Pascal language

The Pascal language was named for Blaise Pascal, a French mathematician who was a pioneer in the history of computer development. In 1641, at the age of eighteen, Pascal built the first arithmetic machine, probably the first computer. He would improve the instrument eight years later. In 1650, Pascal left the world of geometry and physics to devote himself to religious studies or, as Pascal writes, to "contemplate the greatness and misery of man". Pascal died in Paris on August 19, 1662.

The first computers were programmed in machine code and assembly. This type of programming is tedious and error prone, and extremely difficult to understand and modify. Programming is a long and expensive process. High level languages have been developed to solve this problem. High-level languages provide a set of statements that read like a program called a machine code compiler. Pascal is one of those languages.

Other high-level languages developed during the early years of the computer were FORTRAN (1957), COBOL (1959), Algol (1960), APL (1962), BASIC (1964), C (1972) and Ada ( 1983), in the name of some. A problem with many early languages (eg FORTRAN and BASIC) was the heavy reliance on the use of "goto" instructions. The "Goto" instructions tell the computer to jump from one step to another, allowing the computer to skip the steps or go back to repeat the previous steps. This type of sporadic branching increases the difficulty of the debugging code. In addition, languages such as COBOL have been designed with definitions that are too clear, support for weak data structures, and lack of flexibility, making programs tedious to code and difficult to improve.

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

Pascal went well beyond his original design goals, with commercial use of the language often of exceptional academic interest. Pascal provides rich data structures, including both enumerated and registered data types, and defined with pleasant and powerful clarity. It has provided an orthogonal and recursive approach to data structures, with table tables, record tables, folders containing tables, folder files, table files, record files containing record tables , And so on. Pascal's popularity exploded in the 1970s as it was used for writing systems and application software. For this reason, the International Standards Committee has decided that a formal standard is needed to promote the stability of Pascal language (the ISO 7185 Pascal standard was originally published in 1983). By the end of the 1970s, more than 80 computer systems were using Pascal implementations.

One of the most popular Pascal's of the 1970s and early 1980s was UCSD Pascal on the UCSD P-System operating system. 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 Pascal UCSD. As Wirth wrote in his 1985 Turing Conference Award, from Programming Language Design to Construction Computer, "But Pascal has gained a truly widespread recognition only after Ken Bowles in San Diego has acknowledged that the P system might well be put into work on new micro-computers. His efforts to develop an appropriate environment with the built-in compiler, filer, editor and debugger have caused a breakthrough: Pascal has become available to thousands of new computer users who are not overwhelmed by habits acquired or suffocated by desire to stay compatible with the software of the past ".