Introduction to Pascal language

The Pascal language was proposed by Professor N. Wirth of Switzerland in 1971. It is named in honor of the French mathematician Pascal. It is the world's first structured high-level programming language. Structured programming mainly consists of three basic structures (sequential structure, selection structure, and loop structure). Later, some people regarded functions and procedures as the fourth basic structure. These four structures have an entrance and an exit from the outside. The structure is clear and avoids the confusion caused by GOTO statements. In addition, in terms of programming methods, it is advocated to adopt a top-down and step-by-step approach to refinement. That is, dividing a large and complex problem into a number of small and easy-to-solve problems. Each small problem can be divided into smaller problems that are easier to solve. In this way, every small problem is solved, and the whole big problem is solved. This method also provides convenience for multiple people to collaborate on programming.

Because the Pascal language has good structural programming characteristics, it is suitable for teaching, especially for cultivating students to master the top-down and gradually refined structured programming ideas and methods, and to develop good programming skills. design style and habits, therefore, many universities at home and abroad use PASCAL as a programming teaching language.

Its advantages are:

1. Strict structured form

2. Rich and complete data types

3 , high operating efficiency

4, strong error checking ability

Development

In the more than thirty years since the advent of Pascal, there have been many suitable Various versions for different models. The one with the greatest impact is the Turbo Pascal series of software. It is a Pascal compilation system suitable for microcomputers designed and developed by the American Borland Company. The compilation system has developed from version 1.0 launched in 1983 to version 7.0 launched in 1992. Its versions have been continuously updated and its functions have become more complete.

Turbo Pascal language is a compiled programming language. It provides an integrated environment working system that integrates editing, compilation, running, debugging and other functions.

Pascal has 5 main The versions are Unextended Pascal, Extended Pascal, Object-Oriented Extensions to Pascal, Borland Pascal and Delphi Object Pascal. Among them, Unextended Pascal, Extended Pascal and Object-Oriented Extensions to Pascal were created and maintained by the Pascal Standard Committee. Unextended Pascal is similar to the Pascal user manual and report jointly published by Swiss Professor Niklaus Wirth and K.Jensen in 1974, and Extended Pascal has been extended on its basis, adding many new features, all of which belong to the official Pascal standard; Object-Oriented Extensions to Pascal is a technical report published by the Pascal Standards Committee, based on Extended Pascal. Some features have been added to support object-oriented programming, but it is an informal standard. Borland Pascal and Delphi Object Pascal are Pascal languages ​​designed specifically for compilation tools developed by Borland. The former is a traditional high-level language for the Turbo Pascal series for DOS and Turbo Pascal for Windows 3.x. The latter is used for The object-oriented programming languages ​​​​of Delphi for Windows and Kylix for Linux are not formal Pascal standards and are patented. However, due to the powerful functions and popularity of the Turbo Pascal series and Delphi, Borland Pascal and Delphi Object Pascal have become a standard and are familiar to many people.

Impact

PASCAL is an important milestone in the development of high-level languages. The PASCAL language is the first language to systematically embody the structured programming concepts defined by E.W. Dijkstra and C.A.R. Hoare. In 1971, Professor Nicklaus Wirth (N. Wirth) of the Swiss Federal Institute of Technology invented another simple and clear computer language, which is the PASCAL language named after the computer pioneer Pascal. The PASCAL language has rigorous syntax, clear layers, easy to write programs, and strong readability. It is the first structured programming language. It was widely welcomed as soon as it was born and spread quickly from Europe to the United States. Walls also wrote a large number of books on programming, algorithms and data structures throughout his life, for which he won the 1984 Turing Award.

application

In China's Informatics Olympiad, the Pascal programming tool that was more commonly used in the past was Turbo Pascal, and Freepascal became popular in the 20th century. Turbo Pascal is a 16-bit programming tool under DOS. Before the emergence of Delphi, it was the most commonly used Pascal programming tool in the world. It has an advanced compiler with extremely fast compilation speed and powerful yet easy-to-use integrated development. Environment (IDE) is widely popular among microcomputer programmers. It was its emergence that laid the unshakable foundation of Pascal on the DOS/Windows platform. Common versions in the 20th century include Turbo Pascal 5.5, Turbo Pascal 6.0 and Borland Turbo Pascal. with Objects 7.0. Compared with Turbo Pascal 5.5, Turbo Pascal 6.0 is mainly because the IDE is more powerful, and its programming functions have not changed much. It only adds some new functions, such as the ability to embed asm assembly statements. Borland Turbo Pascal with Objects 7.0 (Borland Pascal 7.0 for short) has made a new leap. First, the IDE has been further strengthened and provided with a program browser. Then, the programming functions have been greatly improved, and some very useful new features have been added. The standard subroutine supports relatively complete object-oriented programming functions, and provides three program compilation modes: DOS real mode, DOS protected mode and Windows mode. It can write protected mode applications that can use expanded memory (XMS) or Windows programs running under Windows 3.x also provide an Object Window Library (OWL), which can be used to quickly develop applications with a consistent window interface (DOS or Windows 3.x). Borland Pascal 7.0 was launched in 1992 and was the last version of the Turbo Pascal series under DOS.

The following is the chronicle of Turbo Pascal:

1983 Turbo Pascal 1.0

Turbo Pascal 2.0

Turbo-87 Pascal improves the speed of real number operations and expands Value range

1985 Turbo Pascal 3.0 adds graphics capabilities

Turbo BCD Pascal is particularly suitable for commercial applications

1987 Turbo Pascal 4.0 provides an integrated development environment (IDE) and introduces the unit concept

1988 Turbo Pascal 5.0 adds debugging capabilities

1989 Turbo Pascal 5.5 supports object-oriented programming (OPP)

1990 Turbo Pascal 6.0 provides object-oriented application frameworks and libraries (Turbo Vision)

1992 Turbo Pascal 7.0 object-oriented application system, more complete IDE

Turbo Vision 2.0

1993 Borland Pascal 7.0 develops Object Windows library

(For Windows) Provide support for OLE multimedia application development

1995 Delphi Visual Pascal

In the 20th century, as Turbo Pascal was gradually eliminated, the National Informatics Olympiad Finals (NOI ) and the International Olympiad in Informatics (IOI) have designated Free Pascal as the Pascal programming tool used in the competition. Free Pascal is a 32-bit Pascal programming tool developed by an international organization. It is a shareware and can be used in various operating systems. Depending on the compilation options, it can use Borland Pascal compatible syntax, Delphi 2 Object Pascal syntax, or other syntax to write programs. Because it has a 32-bit compiler, the theoretical memory reaches 4GB, and it is always being updated and developed, so it is more powerful than Borland Pascal and has many features of modern programming, but at the same time it is also very immature and has many problems. loopholes. Free Pascal is in the early stages of development, and there are very few corresponding function libraries. It is far less attractive to programmers than Delphi and Kylix, which have VCL and CLX. However, its characteristics that are different from Turbo Pascal require league players to improve themselves. algorithm (simply put, time is exchanged for space).

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