Any software created using various programming languages. One of these is Pascal, which a fairly large number of users have heard about, however, few of them have even the slightest idea about it.
Pascal is one of the most widely used languages for writing software code, and has served as the basis for the creation of many other languages. He enters school curriculum teaching high school, as well as initial courses in higher educational institutions.
A little history
The father of Pascal is Niklaus Wirth, who was a member of the programming language development committee. He presented his brainchild to the world community in 1969, and as the name for the product he chose the name of the famous scientist Blaise Pascal, who developed the world's first mechanical machine capable of performing the operations of adding two numbers.
For the first time, newspaper headlines mentioned Pascal in 1970, and the text of the articles covered information about the structure of the new programming language, and also revealed its main advantages over the programming languages existing at that time. Among the key advantages were high efficiency and convenient data structuring, which opened up new and broader opportunities for programmers.
Evolution of Pascal
This programming language kept pace with the times and the development of high technologies, so it was constantly improved. So its evolution looks like this:
UCSD Pascal: This version of Pascal is an improvement over the first and was developed in 1978. The main innovation that was implemented in it is the compiler port, thanks to which it became possible to port the code and make changes to the source system.
Object Pascal: is an object extension for basic version Pascal was created by Niklaus Wirth together with Apple.
Turbo Pascal: was developed in 1983 together with programmers from Borland and became the first integrated environment in history. Nevertheless, it is not entirely correct to consider this version revolutionary, since it was based on Odject Pascal, so there were no special differences between them. It is worth noting that based on Turbo Pascal Microsoft company developed its own programming language, however, it turned out to be unsuccessful and could not gain a foothold in the market.
Modern Object Pascal: these days this programming language is very popular and in demand, and is released in a separate edition, which contains all the most best tools and developments. The great popularity of this version of Pascal is due to its excellent compatibility with all existing operating systems today.
Peculiarities
The Pascal programming language stands out among many similar products due to the fact that it implements strict typing and the ability to structure data and variables. Thanks to this, working with program code is very easy, and various syntax errors and incorrect writing of codes and commands are completely eliminated. In addition, Pascal has a simple and intuitive interface, so working with it is comfortable and convenient even for those users who are just starting to take their first steps in programming.
However, it is worth noting that on the path to perfection, the creators of Pascal had to face a large number of different problems and shortcomings, which were eliminated as the language evolved. For example, in the first versions of Pascal there was no ability to work with RAM, and the I/O library was too small, making it impossible to run functions written in other languages.
Flaws
Today there is not a single universal programming language that does not have shortcomings, and Pascal is no exception. In defense of this language, it can be noted that developers are constantly fighting to eliminate them, however, work is progressing extremely slowly for many reasons. However, it is worth noting that many novice programmers made a significant breakthrough at the stage of their formation precisely due to the shortcomings of Pascal.
Nevertheless, despite a fairly decent list of Pascal's shortcomings, this language managed to outperform many of its opponents. For example, with the exit new version in 1980, Pascal was ahead of Fortran by a huge margin, which, by the way, had significantly more shortcomings. Thus, in just a few years, Pascal was able to reliably gain a foothold in the market and win the title of one of best languages programming, and its study has become mandatory in many schools around the world. In addition, most of the programs that can be found on the Internet are created based on Pascal, which already says a lot.
Structure
The program code of any program that is written in Pascal language, begins with a special tag Program, followed by the name of the utility, and at the end there is a punctuation mark “semicolon”. It is worth noting that this condition is not mandatory, so compliance with it is not considered strict. Following this tag, the main operating parameters of the program can be written, which are implemented in the form of a list of configuration files. Next comes the main part of the program code - the body, which is divided into separate blocks containing information about variables, types, procedures, functions and constants. After the body there is an entry point, also called a statement block, placed between the begin and end tags that define its boundaries. To separate operators, use “;”, and to close a block, simply put a dot.
Using modules
To use any modules in the program, you must first declare it. For this purpose, connection instructions are intended, which take the form of a line of regular program code, starting with the word USES, followed by a list of all external modules, which will be used when writing the program. It is worth noting that the ability to use modules is not implemented in all versions of Pascal. For example, the very first editions were deprived of this opportunity.
Punctuation
To create programs in Pascal, you must strictly adhere to the rules of punctuation, otherwise the program code will not execute properly, and the utility itself simply will not work. So, the following punctuation marks are used in Pascal:
- ";" - is intended to separate operators from each other and is placed at the end of the line. It is not required to be used before the closing end tag.
- "," - is responsible for separating different objects within one list.
- "." - placed at the end of the program code after the closing tag.
If the rules for placing punctuation marks are not followed or if they are missed, the user receives a notification about software glitch. Regarding the use of lowercase or capital letters, then the way they are written is not of fundamental importance.
In computer science, Pascal programming language is one of the iconic programming languages that many generations of students have cut their teeth on and variants of which are still widely used today. "TeX" and most of the original operating system"Macintosh" were written in the Pascal programming language.
Programming for beginners. Niklaus Wirth developed it in 1970 for structured programming, which would be easy to compile. The Pascal programming language is based on the Algol programming language and is named after the mathematician and philosopher Blaise Pascal, a pioneer in the world of basic programming. Wirth developed Modula-2 and Oberon, which were similar to Pascal but which began to support object-oriented programming. .
Basic Syntax A typical example of the syntax of the Pascal programming language can be seen in the Hello World program.
PROGRAM HelloWorld; BEGIN WriteLn("Hello world!"); END.
All programs begin with the keyword "PROGRAM" and a block of code is designated by the keywords "BEGIN" / "END". Letter case (lowercase or uppercase) is not case sensitive in Pascal. . Semicolon separated logical expressions, and "END." with a dot at the end ends the main program block. For some keyword compilers, the word PROGRAM is optional. Programming for dummies.
Pascal, in its original form, is a purely procedural language with a standard set compound operators if, while, for and related structures.
Pascal and C
Pascal was developed around the same time as C, so there are important similarities between the two. The original Pascal and C are small, procedural languages that implement the concept of structured programming. Both have functionality for dynamic memory allocation and some instructions for manipulating pointers. But these languages are completely different in appearance, and Xi looks more concise. .
The huge difference is the assignment operator, which is the source of the holy war: Pascal uses ":=" for assignment, and "=" is used for comparison. This contrasts with C's use of x = y for assignment and "==" for comparison. Since the "=" symbol is used in mathematics for both comparison and assignment, the Pascal developer decided that it was better to use ":=" for assignment, since mathematicians are more accustomed to seeing the equal sign (=) as a comparison symbol. The C designer argued that the assignment operator is much more commonly used than the comparison operator, so it should have a short symbol. Pascal supporters retort to this by saying that very often, when using comparison in conditional expressions, programmers mistakenly write an equal sign for comparison.
This discussion reflects differences in the design philosophies of the two languages. Pascal was developed as an educational language. In Pascal, compound operator errors are very rare, and the syntax is made intuitive. Xi's authors paid more attention to brevity.
Another important difference is that Pascal is strongly typed. This means that all variables must be defined at the beginning of the program with a data type before they can be used. In addition, variables of incompatible data types must be explicitly cast to the required data type. This prevents typical mistakes, where variables are used incorrectly because the type is unknown. This also removes the need for Hungarian notation - the practice of specifying the first letter of a variable to be the initial letter of the data type.
Unlike C, Pascal allows you to define variables anywhere in the code. In its original form, Pascal lacked a mechanism for separate compilation or for processing arrays with an unknown size at compile time, but after a couple of versions of the language these problems were eliminated.
Implementations
Early approaches (most notably the UCSD p-System) translated Pascal code into a machine-independent p-code representation. This intermediate code was then interpreted by the program into architecture-specific code. As a consequence, only a small part of the translator has been ported to many architectures.
In the 1980s, Anders Hejlsberg writes the Blue Label Pascal compiler for Nascom-2. He later went to work for Borland and rewrote his compiler to become Turbo Pascal for the IBM PC. This new compiler sold for $49, which was much less than Heilsberg's original asking price for the Blue Label Pascal compiler.
The inexpensive Borland compiler had a major influence on the Pascal community, which began primarily on the IBM PC in late 1980. Many PC enthusiasts looking for a replacement for structured BASIC have used this product. Turbo Pascal, while only available for one architecture, was translated directly onto the Intel 8088 into machine code, making it much faster than the circuit when Pascal was an interpreted language.
In the 1990s, compilers that could be ported to different hardware architectures became more common. This allowed Pascal to be translated into machine code that was at the same time easily portable to new hardware.
With Turbo Pascal version 5, Borland added an object-oriented approach to Pascal.
However, Borland later decided that he wanted more sophisticated object-oriented programming, and work began on Delphi using the Object Pascal standard proposed by Apple as a basis. (This Apple project was not a formal standard at the time.) Borland also called the language Object Pascal in the first version of Delphi, but changed the name to the Delphi Programming Language in later versions. The main changes from the first versions were a pointer-based object model, virtual constructors and destructors, and properties.
Publicly available compilers
Several Pascal compilers are available for use by the general public:
- The GNU Pascal Compiler (GPC) is an additional interface to the GNU Compiler Collection (GCC), and is written in C. freely distributed under the GNU General Public License. Although support for Turbo Pascal (Borland) is somewhat limited.
- FreePascal is written in Pascal (so it compiles itself), and aims to provide a convenient and powerful compiler suitable for compiling older applications while also being a tool for developing new applications. Also freely distributed under the GNU GPL license. It can mix Turbo Pascal with Delphi code and also supports many platforms and operating systems.
- Turbo Pascal was the dominant Pascal compiler for personal computers during the 80s and early 90s, popular both due to its powerful extension and extremely low compilation time. Currently, older versions of Turbo Pascal (up to 5.5) are available for free download from the Borland website (registration required).
- Delphi is Borland's flagship RAD (Rapid Application Development) product. It uses the Delphi programming language, can work with Pascal, and is designed for creating applications for Windows platforms. Latest version also supports compilation in . NET platforms.
- Kylix is Borland's reincarnation of its Pascal product. It is a descendant of Delphi, with operating support Linux systems and an improved object library. The compiler and IDE are now available for non-commercial use. The compiler itself (but libraries or IDE) should become open source software source code soon.
Criticism from the past
Despite its popularity (which peaked in the 1980s and early 1990s), Pascal was widely criticized in its early versions for being unsuitable for "serious" use outside of education. Brian Kernighan, one of the creators of the C programming language, laid out his most notable criticism of Pascal back in 1981, in his article "Why Pascal Isn't My Favorite Programming Language." Since then, Pascal has begun to change, and most of the points that were criticized do not apply to the current implementation.
Many ignorant people still continue to believe that Pascal is not for "serious" programming and do not understand the benefits that this language offers in this moment. This stigma weighs on Pascal more than any real drawback.
Here are a few notes from the history of the Pascal programming language. After reading this article, you will learn what stages the history of the Pascal language took place.
The very name of the language - “Pascal” - arose in honor of one of the great French mathematicians and physicists Blaise Pascal (1623-1662). A little from the life history of the French thinker. Blaise Pascal was born into the family of the famous mathematician Etienne Pascal.
A distinctive feature of all his relatives is their extraordinary talent. He had two sisters: the older sister Gilberte had more developed mathematical abilities and literary talent, and the younger sister Jacqueline had an artistic gift. Blaise Pascal spent his childhood in Paris and never attended school.
The only teacher Pascal recognized was his father Etienne. At the age of four, Blaise already knew how to read and write, began to be interested in Euclidean geometry, and at the age of 15 he could already discuss the most complex mathematical problems with the then famous Parisian scientists. From the youth Pascal grew into a brilliant mathematician.
One of Blaise Pascal's famous inventions was the adding machine (Pascal wheel), which performed all arithmetic operations. It was a brass box with an interesting mechanism (pic. below).
This adding machine made Blaise Pascal famous throughout Western countries. Crowds of people from the old world headed to the Luxembourg Palace (Paris) to see this unique device of that time.
Continues, and in the 50s of the 20th century the first programming languages appeared high level: FORTRAN, COBOL and ALGOL. FORTRAN and COBOL exist to this day, but ALGOL became the founder 
Pascal programming language.
The first version of ALGOL appeared in 1958, developed by the creator of FORTRAN, John Backus. Subsequent versions of the ALGOL language were ALGOL-60 and ALGOL-68. However, due to the cumbersome nature of the ALGOL-60 and ALGOL-68 languages, great difficulties were created.
Therefore, in 1965, the International Federation for Information Processing proposed the project to several computer specialists. It was necessary to create new language programming - successor to ALGOL-60.
The future creator of the Pascal programming language, Nicholas Wirth, a Swiss scientist, at that time an assistant professor at the Faculty of Computer Science at Stanford University, took part in this project.
Nicholas Wirth began developing the ALGOL-W project. The goal of the project was to train students various methods: “structured programming”, “top-down programming”, etc. In 1970, two great events occurred:
- emergence of the UNIX operating system
- the emergence of a new programming language.
Nicholas Wirth named the new programming language after the 17th century French mathematician Blaise Pascal, because Pascal created a computing device (the Pascal wheel). The first version of the new programming language was released on the CDC 6000 computer.
Success of the Pascal language:
The outstanding success of the Pascal language is due to a number of reasons:
- The language reflected in a natural form the most important modern concepts in software development technology.
- It is precisely thanks to its compactness, integrity and orthogonality of concepts that the Pascal programming language turned out to be very easy to learn and master.
- Despite the apparent simplicity of the language, it turned out to be suitable for a fairly wide range of applications, for the development of very large and complex programs, even operating systems.
- Pascal is very technologically advanced for implementing almost all (including non-traditional) machine textures. There is an interesting comparison: developing a Pascal translator is almost no more labor intensive than a good one thesis university graduate.
So, you have seen how the history of the Pascal language unfolded. Are you interested in the article?! Due to its simplicity and lack of cumbersomeness, the basics of the Pascal programming language can be comprehended by both students of higher educational institutions and ordinary schoolchildren. Programming in Pascal is a fun activity. Program and enjoy!
Among the many programming languages designed to teach programming skills, there is one that stands out in particular. The Pascal language, named after the 17th century French scientist Blaise Pascal, was developed in the late 1960s. scientist from Switzerland Niklaus Wirth, and not for educational purposes, as this language is perceived now.
On the contrary, in those days scientists tried different languages programming for practical application. And later, this scientist later created two more programming languages - Oberon and Modula, which, however, did not become widespread among specialists. To be precise, in 1968 the first version of the Pascal language was created (based on ALGOL), and in 1970 the first compiler was created.
A special feature of Pascal is its structural orientation - any program here can be described as a combination of individual structural elements, or blocks, into a single whole. This is the so-called structured programming, which replaced linear programming - the simplest organization of writing programs, when commands are written to the processor one after another, without any structure.
The idea of structured programming turned out to be both relevant at that time and very fruitful, since not for all tasks it is possible to write a program by specifying the sequence simple commands, without separating the latter into separate blocks. Indeed, only if there is a certain program structure can one judge an effective algorithm for solving a problem.
This became especially clear after Professor Hoar published two articles around 1970: “The axiomatic basis of programming for computers" and "On the structural organization of data", in which an attempt is made to understand the correctness of the composition of program algorithms from a mathematical point of view. It is precisely the Pascal programming language that is the first of the languages that has all necessary tools to check the effectiveness of written programs.
One more distinctive feature Pascal is its strict data typing, among which a new previously unused type arose - enumerated. Factor strong typing made Pascal's reputation as a disciplining language that teaches the programmer to think logically.
In Pascal, uncoupledness of the program code is allowed (unlike the COBOL and FORTRAN languages of that time), that is, an arbitrarily large presence of empty lines is allowed, which is convenient for formatting when writing comments. You can write a program in Pascal in just one line - it will still work if it is written in accordance with the rules.
But with the spread of this programming language, it turned out that it lacks many elements familiar to us - exponentiation, the concept of a local variable, dynamic arrays, the ability to use machine language, etc. The most famous expression of this shortcoming of that time is Kernighan’s article “Why Pascal is not my favorite programming language.”
One of the reasons for such dissatisfaction with Pascal at that time was the impossibility of writing a program composed of several parts, since there were simply no mechanisms for this. But Niklaus Wirth and his colleagues, in subsequent releases of Pascal, eliminated all these shortcomings, following all the principles of programming.
The Pascal language, invented in the early 70s of the 20th century by N. Wirth and named after the French mathematician and philosopher Blaise Pascal, is one of the most common programming languages.
vaniya. What sets it apart from other languages is its ability to write programs more clearly and logically.
The Pascal program consists of two parts: a description of the actions,
to be performed and a description of the data on which they are performed
are filling up. In the program text, the description of the data precedes the description of the action.
stiy. This expresses the general rule of the language - every object encountered in a program must be previously described.
The data description consists of the variable description. Operators are called
There are actions on the data. In general, any Pascal program has the form:
program title
variable description section
operators section
The program header looks like:
program program name;
Here the word "program" is the so-called key (or service or they say reserved) word. It must be written exactly
so (without quotes), and not otherwise. Both lowercase and uppercase letters are allowed. The entries PROGRAM, Program, ProgRam are allowed and mean the same thing.
This is how all programs written in Pascal begin. There's nothing here
go understand, it’s just the language developer’s custom.
In principle, it is possible not to use the program header, but it is better to start the program with the header!
A program name is any sequence of letters, numbers and some symbols. Such sequences are called identifiers.
The identifier consists of 1-127 characters - letters, numbers or underscores -
name, and the first must be a letter or an underscore. Identification
The ficator must not match any of the keywords. The identifier should not contain (.) – a period, (, ) – a comma, the brackets themselves (), as well as spaces and operation signs.
Examples of correct identifiers:
Select_screen_color
Examples of incorrect identifiers:
3x starts with a number
Sum.ma there is a dot inside the identifier
VOL VO there is a space
2.1.1 Variables. Standard types.
Each variable has a name and a type. The variable name is an arbitrary identifier. In what follows we will say “variable x” instead of “variable”
variable with the name x ".
2.1 Basic elements of language
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The type of a variable determines the set of its possible values, a set of up to
valid operations on the variable and the size of the occupied memory.
Pascal has the following standard variable types: integer, real, boolean, char
(character), string (string).
The values of variables of integer type are integers (and only!) numbers.
Examples of integers:
Operations on integers are as follows:
+ (addition), - (subtraction), * (multiplication), div (integer division), mod
(remainder of division of two integers).
The values of variables of real type are real numbers.
la. The following operations on real numbers are defined:
+ (addition), - (subtraction), * (multiplication), / (division).
Record real numbers similar to the generally accepted one, only instead of
the fifth is a dot and the letter E is used instead of the power of 10.
The values of Boolean type variables are true, false
(lie). The following operations are defined: not (not), and (and), or (or), xor (exclusive or).
Chapter 2 Introduction to the Pascal Programming Language
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The values of character type variables are single characters. For pre-
To place characters in computer memory, special encoding tables are used, which will be discussed later.
The values of string type variables are a string of characters. When writing constants of character and string types, single quotes are used.
Example.
"A" is the symbol A
"It's a chain of characters"
2.1.2 Relational operations
The following relational operations exist:
Equals,<>not equal,< меньше, >more,<= меньше или равно,
>= greater than or equal to.
The result of these operations is logical true values or false.
2.1.3 Variable descriptions section
This section looks like:
var description 1; description 2; ...; description n;
var – keyword(from English variable - variable)
the description looks like:
variable 1, variable 2, ..., variable m: type;
variable 1, variable 2, ..., variable k: type;
…………………………………………………………
variable 1, variable 2, ..., variable s: type;
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