Dictionary of Pascal

Pascal programming language uses the following set of characters.                                           1)English and Russian letters, which can be both uppercase and lowercase.
2)Arabic numerals.
3)Signs and symbols of operations included in the composite designation of operations:
+ – * / = <>
4)Surge:
. , () [] {}; ‘”
5)Special characters:
@ # $ &% ^ _ ~

To ensure the use of the memory cells are variables.
Variable – the name of the physical memory location in which at any given time can only store one value. To designate areas of memory used identifiers (names).

Identifiers (names of variables, constants, programs, modules, functions, procedures) are written using characters allowed in Pascal and must satisfy the following rules:

1-Name must contain only English letters, digits, and underscores (identifiers in Pascal uppercase and lowercase letters are not distinguished);
2-name can only start with an English letter or an underscore.

Words used in most programming languages​​, including Pascal, divided into three groups: reserved (key) words; predefined names and identifiers are defined by the programmer.

Utilities (reserved, key) words – the words of the programming language, which have a special, once and for all assigned to them meaning. The program can not use the IDs that match the keywords writing (for example, you can not set the variable name begin).

Keywords Pascal programming language:

and end nil set
array file not then
begin for of to
case function or type
const goto packed until
div if procedure var
do in program while
downto label record with
else mod repeat

Predefined (standard) names also have special (predefined) meaning. However, the programmer can get the values ​​assigned to them and use them as names defined by the programmer. If the programmer does not explicitly define the purposes for which it is used or otherwise the default name in the program, it will be seen in its proper sense, given the name of a predefined (eg, predefined names are Integer, Writeln et al.).

User names are defined by the programmer and must be declared in the program.

Decimal numbers always begin with a digit in front of which can be a sign of the number, + or -.

Real numbers are represented in two formats. In the fixed-point format clearly indicate the position of the decimal point (eg, 4.505, -16.25, +1.0). In floating-point format is used a decimal scale, denoted uppercase or lowercase letter E, after which there is an integer indicating the value of the order, for example, 8e10, 1.62e-3, 0.8E + 3.

In Pascal, the maximum integer equal to 2147483647 (it is contained in a predefined integer constant MaxLongInt). To get this number is sufficient to perform the expression

writeln (maxlongint);
Range of integers from -2147483647 to 2147483647 predefined integer constant in Pascal MaxInt contains the value 32767

writeln (maxint);
Common Pascal compilers allow you to operate the real numbers to 38 order, and some – up to 67 orders of magnitude.

An integer can be specified not only in decimal, but in hexadecimal. Hexadecimal number preceded by the $ sign.

Text literal (string) in Pascal is a sequence of any valid characters that stand between apostrophes (for example, ‘Hello World!’). If the character string is necessary to use an apostrophe, then recorded two consecutive apostrophes

writeln (‘Don”t do it’)
String can be specified as a sequence formed from a character # followed by a numerical code of the desired character (for example, record # 72 # 73 # 33 is equivalent to the string ‘HI!’). In the string data uppercase and lowercase letters are different.

Spaces are stripped. Between any of the names, numbers, the keyword should be at least one splitter, and they can be and how much you want. But it is impossible to separate one character from another within a name, number or keyword.

 

History and features of the programming language Pascal (Pascal)

Among the many programming language stand dozens of languages​​, which are widely used and spread in certain segments of the computer history. In this group of widely spoken languages ​​include programming language Pascal.

It has long been accepted that it is good for learning programming. Indeed. Pascal language was created in the late 60s N. Wirth as a special language for teaching students. Soon, however, due to the implementation of the progressive ideas of the time became popular among programmers. There was a time when Pascal was widely used for writing application programs, and even as a system programming language. Software many mini and microcomputers was written in Pascal.

At birth, a programming language into the light should appear as a description, and a translator from it into machine code. After a 70-year Pascal language developed and improved, included new features. Produce new compilers and development environment for Pascal

Translators with this language had on the most common types of computers around the world. Availability of special techniques for building compilers for Pascal simplify their development and contributed to the widespread dissemination of the language. Compilers can optimize the code, and it allows you to create effective programs. It just was one of the reasons for the use of Pascal as a systems programming language.

In the 80s began to enter computer science to the masses, there was the subject of “science”. Since that time, Pascal was very fashionable and has established itself as an academic language, it is widely spread in schools and universities. In the end, it was written a lot of tutorials on the language.

To be more simple, Pascal has some limitations. Thus, Pascal well “teaches” to understand how the data is stored in the computer’s memory, but has some limitations when working with them (which is devoid of most of the “real” languages).

Because Pascal once actively used to solve practical problems, based on it produced an Object Pascal (which is now used in Delphi).

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Basic rules of grammar

Text of the program consists of three parts. This is the title, description, operators. The program header contains the name of the program. For ETH version, you must specify the source and destination data for the program – files for input and output. By default, the input file is associated with a computer keyboard, and file output – to the monitor screen. In Turbo Pascal header has ornamental value and its use is not mandatory.

Descriptions – are symbolic structures for describing the properties of objects in the program. All objects of the program it is necessary to specify in this part of the program. Operators – this character design for the description of the program of action on objects. Operators must be between the words begin and end. These words are considered staples

In one line of text, you can place multiple statements or descriptions. Therefore, it is necessary between operators to put a separator character. Used to separate statements with a semicolon (;). After the last statement does not necessarily put a separator.

Small and large letters are considered equivalent to (equivalent). The name of any object in the program recording may contain only letters, numbers, and the underscore character (_). The name can not start with a digit. No other types of characters in the record names are not allowed.

Pascal

Pascal (named after Blaise Pascal) – this is a purely procedural programming language often used for teaching structured programming.

Pascal was developed by Niklaus Wirth in 1970; contrary to popular belief, he was not only learning the language and intended for practical use. Served as the prototype Algol. The original language is compiled into byte code language like Java.

In 1983 he passed the first language standard, ISO 7185:1983, which is also called Standard Pascal. This standard does not add new elements to the language, but only formally described the existing features of the language. In 1990 he was accepted standard ISO / IEC 10206, defines the so-called Extended Pascal. The main change was the addition of modularity.

Features of the language is strongly typed and the availability of structural (procedural) programming. Pascal was one of the first such language. According to N. Wirth language had to contribute to the discipline of programming, however, along with the strong typing in Pascal minimized possible syntactic ambiguity, and the syntax is intuitive, even on first acquaintance with the language. It is easier to write compilers.

Moreover, the language provides a number of built-in data structures: records, arrays, files, and set pointers.

Nevertheless, the original language has many drawbacks: the inability to transfer functions varrays, lack of normal means of dynamic memory, limited IO library, lack of funds to connect the functions written in other languages​​, the lack of separate compilation, etc.

Dialect of Object Pascal, developed in 1985, supports object-oriented programming. There are several modern compilers and language currently quite popular.

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