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{{Infobox programming language
| name = Pascal
| logo = 
| paradigm = {{hlist |[[Imperative programming|Imperative]] |[[Structured programming|Structured]]}}
| typing = {{hlist |[[Static typing|Static]] |[[Strong and weak typing|Strong]] |[[type system#Type safety and memory safety|Safe]]}}
| implementations = {{hlist |[[CDC 6000]] | |[[Delphi (programming language)|Embarcadero Delphi]] |[[ICT 1900 series|ICL 1900]] |[[Pascal-P]] |[[PDP-11]] |[[PDP-10]] |[[IBM System/370]] |[[HP Pascal]] |[[Free Pascal]] |[[GNU Pascal]]}}
| dialects = {{hlist |[[Delphi (programming language)|Delphi]] |[[Turbo Pascal]] |[[UCSD Pascal]]}}
| year = {{Start date and age|1970}}
| designer = [[Niklaus Wirth]]
| latest release version = | latest release date = 
| influenced_by = [[ALGOL W]]
| influenced = {{startflatlist}}
* [[Ada (programming language)|Ada]]
* [[Component Pascal]]
* [[Go (programming language)|Go]]
* [[Java (programming language)|Java]]<ref>"We looked very carefully at Delphi [[Object Pascal]] and built a working prototype of bound method references in order to understand their interaction with the Java programming language and its APIs&nbsp;... Our conclusion was that bound method references are unnecessary and detrimental to the language. This decision was made in consultation with Borland International, who had previous experience with bound method references in Delphi [[Object Pascal]]." (from [http://java.sun.com/docs/white/delegates.html About Microsoft's "Delegates"] at java.sun.com.</ref><ref>{{cite web |url=http://www.fscript.org/prof/javapassport.pdf |quote=The project went ahead under the name "green" and the language was based on an old model of [[UCSD Pascal]], which makes it possible to generate interpretive code |title=History of Java |work=Java Application Servers Report |author=TechMetrix Research |year=1999}}</ref><ref>{{cite web|url=http://queue.acm.org/detail.cfm?id=1017013|title=A Conversation with James Gosling - ACM Queue|publisher=|accessdate=11 August 2015}}</ref>
* [[Modula]]{{\}}[[Modula-2|-2]]{{\}}[[Modula-3|-3]]
* [[Oberon (programming language)|Oberon]]{{\}}[[Oberon-2 (programming language)|-2]]
* [[Object Pascal]]
* [[Oxygene (programming language)|Oxygene]]
* [[Seed7]]
{{endflatlist}}
| operating_system = 
| license = 
| file ext = <code>.pp</code>, <code>.pas</code>, <code>.inc</code>,
| website = 
}}

'''Pascal''' is an [[Imperative programming|imperative]] and [[Procedural programming|procedural]] [[programming language]], which [[Niklaus Wirth]] designed in 1968–69 and published in 1970, as a small, efficient language intended to encourage good programming practices using [[structured programming]] and [[data structure|data structuring]]. It is named in honor of the French mathematician, philosopher and physicist [[Blaise Pascal]].

Pascal was developed on the pattern of the [[ALGOL 60]] language. Wirth had already developed several improvements to this language as part of the [[ALGOL X]] proposals, but these were not accepted and Pascal was developed separately and released in 1970. A derivative known as [[Object Pascal]] designed for [[object-oriented programming]] was developed in 1985; this was used by [[Apple Computer]] and [[Borland]] in the late 1980s and later developed into [[Delphi (programming language)|Delphi]] on the [[Microsoft Windows]] platform. Extensions to the Pascal concepts led to the Pascal-like languages [[Modula-2]] and [[Oberon (programming language)|Oberon]].

==History==
===Earlier efforts===
Much of the history of [[computer language]] design during the 1960s traces its history to the [[ALGOL 60]] language. ALGOL was developed during the 1950s with the explicit goal to be able to clearly describe algorithms. It included a number of features for [[structured programming]] that remain common in languages to this day.

Shortly after its introduction, in 1962 Wirth began working on his dissertation with Helmut Weber on the [[Euler (programming language)|Euler programming language]]. Euler was based on ALGOL's syntax and many concepts but was not a derivative. Its primary goal was to add dynamic lists and types, allowing it to be used in roles similar to the [[Lisp (programming language)|Lisp]]. The language was published in 1965.

By this time, a number of problems in ALGOL had been identified, notably the lack of a standardized [[String (computer science)|string]] system. The group tasked with maintaining the language had begun the [[ALGOL X]] process to identify improvements, calling for submissions. Wirth and [[Tony Hoare]] submitted a conservative set of modifications to add strings and clean up some of the syntax. These were considered too minor to be worth using as the new standard ALGOL, so Wirth wrote a compiler for the language, which became known as [[ALGOL W]].

The ALGOL X efforts would go on to choose a dramatically more complex language, [[ALGOL 68]]. The complexity of this language led to considerable difficulty producing high-performance compilers, and it was not widely used in the industry. This left an opening for newer languages.

===Pascal===
Pascal was influenced by the ALGOL W efforts, with the explicit goals of producing a language that would be efficient both in the compiler and at run-time, allow for the development of well-structured programs, and to be useful for teaching students [[structured programming]].<ref>[http://www.marcocantu.com/epascal/English/ch01hist.htm Essential Pascal] by Marco Cantù</ref> A generation of students used Pascal as an introductory language in undergraduate courses.

One of the early successes for language was the introduction of [[UCSD Pascal]], a version that ran on a custom [[operating system]] that could be ported to different platforms. A key platform was the [[Apple II]], where it saw widespread use. This led to the use of Pascal becoming the primary high-level language used for development in the [[Apple Lisa]], and later, the [[Apple Macintosh|Macintosh]]. Parts of the original [[Classic Mac OS|Macintosh operating system]] were hand-translated into [[Motorola 68000]] [[assembly language]] from the Pascal sources.<ref>Hertzfeld, Andy. "[http://www.folklore.org/StoryView.py?project=Macintosh&story=Hungarian.txt&topic=Software%20Design&sortOrder=Sort%20by%20Date&detail=medium Hungarian folklore.org]: Macintosh Stories. Retrieved 2012-03-06.</ref>

The [[typesetting]] system [[TeX]] by [[Donald E. Knuth]] was written in [[WEB]], the original [[literate programming]] system, based on [[Digital Equipment Corporation|DEC]] [[PDP-10]] Pascal, while applications like [[Total Commander]], [[Skype]] and Macromedia Captivate were written in Delphi ([[Object Pascal]]). [[Apollo Computer]] used Pascal as the systems programming language for its operating systems beginning in 1980.

Variants of Pascal have also frequently been used for everything from research projects to [[PC game]]s and [[embedded systems]]. Newer Pascal compilers exist which are widely used.<ref>[http://www.tiobe.com/index.php/content/paperinfo/tpci/ tiobe.com], Programming Community Index for January 2011.</ref>

===Object Pascal===
During work on the Lisa, [[Larry Tesler]] began corresponding with Wirth on the idea of adding [[object oriented]] extensions to the language. This led initially to [[Clascal]], introduced in 1983. As the Lisa program faded and was replaced by the Mac, a further version known as [[Object Pascal]] was created. This was introduced on the Macintosh in 1985 as part of the [[MacApp]] [[application framework]], and became Apple's primary development language into the early 1990s.

The Object Pascal extensions were later added to [[Turbo Pascal]], and over the years became the [[Delphi (programming language)|Delphi]] system for [[Microsoft Windows]]. Delphi is still used for developing Windows applications, but also has the ability to cross-compile the same code to Mac, iOS and Android. Another cross-platform version called [[Free Pascal]], with the [[Lazarus (IDE)|Lazarus]] IDE, is popular with Linux users since it also offers [[write once, compile anywhere]] development. CodeTyphon is a Lazarus distribution with more preinstalled packages and cross-compilers.

==Brief description==
Wirth's intention was to create an efficient language (regarding both compilation speed and generated code) based on [[structured programming]], a recently popularized concept that he promoted in his book ''[[Algorithms + Data Structures = Programs]]''. Pascal has its roots in the [[ALGOL 60]] language, but also introduced concepts and mechanisms which (on top of ALGOL's scalars and arrays) enabled programmers to define their own complex (structured) datatypes, and also made it easier to build dynamic and recursive data structures such as ''lists'', ''trees'' and ''graphs''. Important features included for this were ''records'', ''enumerations'', ''subranges'', ''dynamically'' allocated variables with associated ''pointers'', and ''sets''. To make this possible and meaningful, Pascal has a [[strong typing]] on all objects, which means that one type of data cannot be converted or interpreted as another without ''explicit'' conversions. Similar mechanisms are standard in many programming languages today. Other languages that influenced Pascal's development were [[Simula]] 67 and Wirth's own [[ALGOL W]].

Pascal, like many programming languages of today (but unlike most languages in the C family), allows [[nested procedure]] definitions to any level of depth, and also allows most kinds of definitions and declarations inside [[subroutines]] (procedures and functions). This enables a very simple and coherent syntax where a complete ''program'' is syntactically nearly identical to a single ''procedure'' or ''function'' (except for the heading, which has one of these three keywords).

==Implementations==

===Early Pascal compilers===
The first Pascal [[compiler]] was designed in [[Zürich]] for the [[CDC 6000 series]] [[mainframe computer]] family. [[Niklaus Wirth]] reports that a first attempt to implement it in [[Fortran]] in 1969 was unsuccessful due to Fortran's inadequacy to express complex data structures. The second attempt was implemented in a C-like language (Scallop by Max Engeli) and then translated by hand (by R. Schild) to Pascal itself for boot-strapping.<ref>[https://www.inf.ethz.ch/personal/wirth/Miscellaneous/ComputersAndComputing.pdf Computers and Computing. A Personal Perspective.] by Niklaus Wirth</ref> It was operational by mid-1970. Many Pascal compilers since have been similarly [[self-hosting]], that is, the compiler is itself written in Pascal, and the compiler is usually capable of recompiling itself when new features are added to the language, or when the compiler is to be [[porting|ported]] to a new environment.  The [[GNU Pascal]] compiler is one notable exception, being written in C.

The first successful port of the CDC Pascal compiler to another mainframe was completed by Welsh and Quinn at the [[Queen's University of Belfast]] (QUB) in 1972.  The target was the [[International Computers Limited|ICL]] [[ICT 1900 series|1900 series]]. This compiler, in turn, was the parent of the Pascal compiler for the Information Computer Systems (ICS) [[Multum]] minicomputer. The Multum port was developed&nbsp;– with a view to using Pascal as a systems programming language&nbsp;– by Findlay, Cupples, Cavouras and Davis, working at the Department of Computing Science in [[Glasgow University]]. It is thought that Multum Pascal, which was completed in the summer of 1973, may have been the first 16-bit implementation.

A completely new compiler was completed by Welsh et al. at QUB in 1977. It offered a source-language diagnostic feature (incorporating profiling, tracing and type-aware formatted postmortem dumps) that was implemented by Findlay and Watt at Glasgow University. This implementation was ported in 1980 to the [[ICL 2900]] series by a team based at [[Southampton University]] and Glasgow University. The Standard Pascal Model Implementation was also based on this compiler, having been adapted, by Welsh and Hay at [[Manchester University]] in 1984, to check rigorously for conformity to the BSI 6192/ISO 7185 Standard and to generate code for a portable abstract machine.

The first Pascal [[compiler]] written in North America was constructed at the [[University of Illinois at Urbana-Champaign|University of Illinois]] under [[Donald B. Gillies#Later career|Donald B. Gillies]] for the [[PDP-11]] and generated native machine code.

==={{anchor|Pascal-P}}The Pascal-P system===
To propagate the language rapidly, a compiler "porting kit" was created in Zurich that included a compiler that generated code for a "virtual" stack machine, ''i.e.'', code that lends itself to reasonably efficient interpretation, along with an interpreter for that code&nbsp;– the ''Pascal-P'' system.  The P-system compilers were termed Pascal-P1, Pascal-P2, Pascal-P3, and Pascal-P4. Pascal-P1 was the first version, and Pascal-P4 was the last to come from Zurich. The version termed Pascal-P1 was coined after the fact for the many different sources for Pascal-P that existed. The compiler was redesigned to enhance portability, and issued as Pascal-P2. This code was later enhanced to become Pascal-P3, with an intermediate code [[backward compatible]] with Pascal-P2, and Pascal-P4, which was not backward compatible.

The Pascal-P4 compiler/interpreter can still be run and compiled on systems compatible with original Pascal. However, it only accepts a subset of the Pascal language.

Pascal-P5, created outside the Zurich group, accepts the full Pascal language and includes ISO 7185 compatibility.

[[UCSD Pascal]] branched off Pascal-P2, where [[Kenneth Bowles]] utilized it to create the [[Interpreter (computing)|interpretive]] [[UCSD Pascal|UCSD p-System]]. The UCSD p-System was one of three operating systems available at the launch of the original [[IBM Personal Computer]].<ref>[http://www.cbi.umn.edu/oh/pdf/oh392jb.pdf "An Interview with JOHN BRACKETT AND DOUG ROSS"], p15, Charles Babbage Institute, 2004</ref> UCSD Pascal used an intermediate code based on byte values, and thus was one of the earliest "byte code compilers". Pascal-P1 through Pascal-P4 was not, but rather based on the CDC 6600 60 bit word length.

A compiler based on the Pascal-P4 compiler, which created native binaries, was released for the [[IBM System/370]] [[mainframe computer]] by the [[Australian Atomic Energy Commission]]; it was called the "AAEC Pascal Compiler" after the abbreviation of the name of the Commission.<ref>[http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/10/477/10477561.pdf "AUSTRALIAN ATOMIC ENERGY COMMISSION RESEARCH ESTABLISHMENT, LUCAS HEIGHTS, NUCLEAR SCIENCE AND TECHNOLOGY BRANCH REPORT 1977, DIVISIONAL RESEARCH"], p.22, International Atomic Energy Agency (IEAE)</ref>

In the early 1980s, [[Watcom]] Pascal was developed, also for the IBM [[System 370]].

Into the 1990s, Pascal was still running on [[VAX]] terminals at [[George Mason University]] to teach computer programming.

===Object Pascal and Turbo Pascal===
Apple Computer created its own Lisa Pascal for the Lisa Workshop in 1982, and ported the compiler to the Apple Macintosh and [[Macintosh Programmer's Workshop|MPW]] in 1985.  In 1985 [[Larry Tesler]], in consultation with Niklaus Wirth, defined Object Pascal and these extensions were incorporated in both the Lisa Pascal and Mac Pascal compilers.

In the 1980s, [[Anders Hejlsberg]] wrote the Blue Label Pascal compiler for the [[Nascom]]-2. A reimplementation of this compiler for the [[IBM PC]] was marketed under the names Compas Pascal and PolyPascal before it was acquired by [[Borland]] and renamed ''Turbo Pascal''.

[[Turbo Pascal]] became hugely popular, thanks to an aggressive pricing strategy, having one of the first full-screen [[integrated development environment]]s, and very fast turnaround time (just seconds to compile, link, and run). It was written and highly optimized entirely in [[assembly language]], making it [[Memory footprint|smaller]] and faster than much of the competition.

In 1986, Anders ported Turbo Pascal to the Macintosh and incorporated Apple's Object Pascal extensions into Turbo Pascal.  These extensions were then added back into the PC version of Turbo Pascal for version 5.5. At the same time [[Microsoft]] also implemented the Object Pascal compiler.<ref>Jon Udell, Crash of the Object-Oriented Pascals, BYTE, July, 1989.</ref><ref>M.I.Trofimov, The End of Pascal?, BYTE, March, 1990, p.36.</ref> Turbo Pascal 5.5 had a large influence on the Pascal community, which began concentrating mainly on the IBM PC in the late 1980s.  Many PC hobbyists in search of a structured replacement for BASIC used this product.  It also began to be adopted by professional developers.  Around the same time a number of concepts were imported from [[C (programming language)|C]] to let Pascal programmers use the C-based [[Application programming interface|API]] of [[Microsoft Windows]] directly.  These extensions included null-terminated [[string (computer science)|string]]s, [[pointer arithmetic]], [[function pointer]]s, an address-of operator and unsafe [[type conversion|typecasts]].

Turbo Pascal, and other derivatives with [[Unit (Software Development)|units]] or module concepts are [[modularity (programming)|modular languages]]. However, it does not provide a nested module concept or qualified import and export of specific symbols.

==={{anchor|Pascal-SC|Pascal-XSC}}Other variants===
[[Super Pascal]] was a variant that added non-numeric labels, a return statement and expressions as names of types.

The universities of Wisconsin-Madison, [[Zürich]], [[Karlsruhe]] and [[Wuppertal]] developed the ''Pascal-SC''<ref>{{cite journal | doi = 10.1016/0898-1221(87)90181-7 | volume=14 | title=An introduction to the scientific computing language Pascal-SC | journal=Computers | pages=53–69}}</ref><ref name="Cadmus_1986">{{cite journal |title=Cadmus jetzt mit Kulisch-Arithmetik - Uni Karlsruhe gibt Pascal-Compiler nach München |trans-title=Cadmus now comes with Kulisch arithmetic - University Karlsruhe delivers Pascal compiler to Munich |author=PI |date=1986-08-29 |journal=[[Computerwoche]] |publisher=[[IDG Business Media GmbH]] |language=German |location=Munich / Karlsruhe, Germany |url=http://www.computerwoche.de/a/uni-karlsruhe-gibt-pascal-compiler-nach-muenchen-cadmus-jetzt-mit-kulisch-arithmetik,1165749 |access-date=2016-05-30 |dead-url=no |archive-url=https://web.archive.org/web/20160530220339/http://www.computerwoche.de/a/uni-karlsruhe-gibt-pascal-compiler-nach-muenchen-cadmus-jetzt-mit-kulisch-arithmetik,1165749 |archive-date=2016-05-30}}</ref> and ''Pascal-XSC''<ref>{{cite web |url=http://www.rz.uni-karlsruhe.de/~iam/html/language/pxsc.html |title=PASCAL-XSC: PASCAL for Extended Scientific Computing}}</ref><ref>{{cite web |url=http://www.xsc.de/ |title=XSC Software |accessdate=11 August 2015}}</ref><ref>{{cite web |url=http://www2.math.uni-wuppertal.de/wrswt/xsc/pxsc_download.html |title=Universitaet Wuppertal: Wissenschaftliches Rechnen / Softwaretechnologie |accessdate=11 August 2015}}</ref> (''[[Extensions for Scientific Computation]]'') compilers, aimed at programming numerical computations. [[TMT Pascal]] the first [[Borland]]-compatible compiler for 32-bit [[DOS]] protected mode, [[OS/2]] and [[Win32]] operating systems. Also the TMT Pascal language was the first one which allowed function and [[operator overloading]]. Development for Pascal-SC started in 1978 supporting ISO 7185 Pascal level 0, but level 2 support was added at a later stage.<ref name="Wallis_1990">{{cite book |title=Improving Floating-Point Programming |editor-first=Peter J. L. |editor-last=Wallis |author-first1=Lothar |author-last1=Bamberger |author-first2=James H. |author-last2=Davenport |author-first3=Hans-Christoph |author-last3=Fischer |author-first4=Jan |author-last4=Kok |author-first5=Günter |author-last5=Schumacher |author-first6=Christian |author-last6=Ullrich |author-first7=Peter J. L. |author-last7=Wallis |author-first8=Dik T. |author-last8=Winter |author-first9=Jürgen |author-last9=Wolff von Gudenberg |date=1990 |edition=1st |publisher=[[John Wiley & Sons Ltd.]] |location=Bath, United Kingdom |isbn=0-471-92437-7 <!--|ISBN=978-0-471-92437-1 -->}}</ref> Pascal-SC originally targeted the [[Z80]] processor, but was later rewritten for DOS ([[x86]]) and [[68000]]. Pascal-XSC has at various times been ported to Unix (Linux, [[SunOS]], [[HP-UX]], [[AIX]]) and Microsoft/IBM (DOS with [[EMX (programming environment)|EMX]], OS/2, [[Windows]]) operating systems. It operates by generating intermediate C source code which is then compiled to a native executable. Some of the Pascal-SC language extensions have been adopted by [[GNU Pascal]].

[[Pascal Sol]] was designed around 1983 by a French team to implement a Unix-like systems named Sol.  It was standard Pascal level-1 (with parametrized array bounds) but the definition allowed alternative keywords and predefined identifiers in French and the language included a few extensions to ease system programming (e.g. an equivalent to lseek).<ref>Michel Gien, "The SOL Operating System", in Usenix Summer '83 Conference, Toronto, ON, (July 1983), pp. 75-78</ref> The Sol team later on moved to the [[ChorusOS]] project to design a distributed operating system.<ref>[http://www.cs.berkeley.edu/~prabal/resources/osprelim/RAA+92.pdf cs.berkeley.edu]</ref>

[[IP Pascal]] was an implementation of the Pascal programming language using [[Micropolis (company)|Micropolis]] DOS, but was moved rapidly to [[CP/M-80]] running on the Z80. It was moved to the [[80386]] machine types in 1994, and exists today as Windows/XP and Linux implementations. In 2008, the system was brought up to a new level and the resulting language termed "Pascaline" (after [[Pascal's calculator]]). It includes objects, namespace controls, [[dynamic array]]s, along with many other extensions, and generally features the same functionality and type protection as [[C Sharp (programming language)|C#]]. It is the only such implementation that is also compatible with the original Pascal implementation, which is standardized as ISO 7185.

Smart Mobile Studio<ref>http://smartmobilestudio.com</ref> was created by Jon Aasenden and compiles his own dialect of Object Pascal to HTML5/Javascript

[http://smartmobilestudio.com Smart Mobile Studio] has an IDE which includes a visual component set, its language is unusual in that it incorporates extensions for the Javascript language

==Language constructs==
Pascal, in its original form, is a purely [[procedural language]] and includes the traditional array of [[ALGOL]]-like control structures with reserved words such as '''if''', '''then''', '''else''', '''while''', '''for''', and '''case''' ranging on a single statement or a '''begin'''-'''end''' statements block. Pascal also has data structuring constructs not included in the original [[ALGOL 60]] [[type system|types]], like [[Record (computer science)|record]]s, variants, [[pointer (computer programming)|pointer]]s, [[enumerated type|enumeration]]s, and [[set (computer science)|set]]s and procedure/pointers. Such constructs were in part inherited or inspired from [[Simula]] 67, [[ALGOL 68]], [[Niklaus Wirth]]'s own [[ALGOL W]] and suggestions by [[C. A. R. Hoare]].

Pascal programs start with the '''program''' [[keyword (computer programming)|keyword]] with a list of external [[file descriptor]]s as parameters<ref name="iso/iec 7185:1990 6.10">[http://www.moorecad.com/standardpascal/iso7185.pdf Pascal ISO 7185:1990] 6.10</ref> (not required in Turbo Pascal etc.); then follows the main [[block (programming)|block]] bracketed by the '''begin''' and '''end''' keywords. [[Semicolon]]s separate [[Statement (programming)|statements]], and the [[full stop]] (i.e., a period) ends the whole program (or ''unit''). [[Letter case]] is ignored in Pascal source.

Here is an example of the source code in use for a very simple [["Hello world" program]]:

<source lang=pascal>
program HelloWorld(output);
begin
  Write('Hello, world!')
  {no ";" is required after the last statement of a block -
   adding one adds a "null statement" to the program;}
end.
</source>

===Data types===
A type in Pascal, and in several other popular programming languages,  defines a variable in such a way that it defines a range of values which the variable is capable of storing, and it also defines a set of operations that are permissible to be performed on variables of that type. The predefined types are:

{| class="wikitable"
|-
! Data type
! Type of values which the variable is capable of storing
|-
| [[integer (computer science)|integer]]
| integer (whole) numbers
|-
| [[floating point|real]]
| floating-point numbers
|-
| [[boolean type|boolean]]
| the value True or False
|-
| [[character (computing)|char]]
| a single character from an ordered character set
|-
| [[string (computer science)|string]]
| a group or "string" of characters
|}

The range of values allowed for each (except boolean) is implementation defined. Functions are provided for some data conversions. For conversion of <code>real</code> to <code>integer</code>, the following functions are available: <code>round</code> (which rounds to integer using [[banker's rounding]]) and <code>trunc</code> (rounds towards zero).

The programmer has the freedom to define other commonly used data types (e.g. byte, string, etc.) in terms of the predefined types using Pascal's type declaration facility, for example

<source lang="pascal">
type
  byte        = 0..255;
  signed_byte = -128..127;
  string      = packed array[1..255] of char;
</source>

(Often-used types like byte and string are already defined in many implementations.)

===Subrange types===
Subranges of any [[ordinal data type]] (any simple type except real) can also be made:

<source lang="pascal">
var
  x : 1..10;
  y : 'a'..'z';
</source>

===Set types===
In contrast with other programming languages from its time, Pascal supports a set type:

<source lang="pascal">
var
  Set1 : set of 1..10;
  Set2 : set of 'a'..'z';
</source>

A set is a fundamental concept for modern mathematics, and they may be used in many algorithms. Such a feature is useful and may be faster than an equivalent construct in a language that does not support sets. For example, for many Pascal compilers:

<source lang="pascal">
if i in [5..10] then ...
</source>

executes faster than:

<source lang="pascal">
if (i > 4) and (i < 11) then ...
</source>

Sets of non-contiguous values can be particularly useful, in terms of both performance and readability:

<source lang="pascal">
if i in [0..3, 7, 9, 12..15] then ...
</source>

For these examples, which involve sets over small domains, the improved performance is usually achieved by the compiler representing set variables as bit vectors. The set [[Operator (programming)|operators]] can then be implemented efficiently as bitwise machine code operations.

===Type declarations===
Types can be defined from other types using type declarations:

<source lang="pascal">
type
  x = integer;
  y = x;
...
</source>

Further, complex types can be constructed from simple types:

<source lang="pascal">
type
  a = array[1..10] of integer;
  b = record
        x : integer;
        y : char
      end;
  c = file of a;
</source>

===File type===
As shown in the example above, Pascal [[Computer file|files]] are sequences of components. Every file has a buffer variable which is denoted by ''f^''. The procedures ''get'' (for reading) and ''put'' (for writing) move the buffer variable to the next element. Read is introduced such that ''read(f, x)'' is the same as ''x := f^;  get(f);''. Write is introduced such that ''write(f, x)'' is the same as ''f^ := x;  put(f);'' The type text is predefined as file of char. While the buffer variable could be used for inspecting the next character to be used (check for a digit before reading an integer), this leads to serious problems with interactive programs in early implementations, but was solved later with the "lazy I/O" concept.

In Jensen & Wirth Pascal, strings are represented as packed arrays of chars; they therefore have fixed length and are usually space-padded.

===Pointer types===
Pascal supports the use of [[pointer (computer programming)|pointer]]s:

<source lang="pascal">
type
  pNode = ^Node;
  Node  = record
          a : integer;
          b : char;
          c : pNode  {extra semicolon not strictly required}
          end;
var
  NodePtr : pNode;
  IntPtr  : ^integer;
</source>

Here the variable ''NodePtr'' is a pointer to the data type ''Node'', a record. Pointers can be used before they are declared. This is a [[forward declaration]], an exception to the rule that things must be declared before they are used.

To create a new record and assign the value ''10'' and character ''A'' to the fields ''a'' and ''b'' in the record, and to initialise the pointer ''c'' to [[Null pointer|NIL]], the commands would be:

<source lang="pascal">
New(NodePtr);
...
NodePtr^.a := 10;
NodePtr^.b := 'A';
NodePtr^.c := NIL;
...
</source>

This could also be done using the '''with''' statement, as follows:

<source lang="pascal">
New(NodePtr);
...
with NodePtr^ do
begin
  a := 10;
  b := 'A';
  c := NIL
end;
...
</source>

Inside of the scope of the ''with'' statement, a and b refer to the subfields of the record pointer ''NodePtr'' and not to the record Node or the pointer type pNode.

[[Linked list]]s, [[Stack (abstract data type)|stacks]] and [[Queue (abstract data type)|queues]] can be created by including a pointer type field (c) in the record (see also [[null pointer|NIL]]).

Unlike many languages that feature pointers, Pascal only allows pointers to reference dynamically created variables that are anonymous, and does not allow them to reference standard static or local variables. Pointers also must have an associated type, and a pointer to one type is not compatible with a pointer to another type (e.g. a pointer to a char is not compatible with a pointer to an integer). This helps eliminate the type security issues inherent with other pointer implementations, particularly those used for [[PL/I]] or [[C (Programming Language)|C]]. It also removes some risks caused by [[dangling pointers]], but the ability to dynamically deallocate referenced space by using the ''dispose'' function (which has the same effect as the ''free'' library function found in [[C (Programming Language)|C]]) means that the risk of dangling pointers has not been entirely eliminated<ref name="Hoare.Sneeringer.Welsh.1977">J. Welsh, W. J. Sneeringer, and C. A. R. Hoare, "Ambiguities and Insecurities in Pascal", ''Software Practice and Experience 7'', pp. 685–696 (1977)</ref> as it has in languages such as Java and C#, which provide [[garbage collection (computer science)|automatic garbage collection]] (but which do not entirely eliminate the related problem of [[memory leak]]s).

Some of these restrictions can be lifted in newer dialects.

===Control structures===
Pascal is a [[structured programming]] language, meaning that the flow of control is structured into standard [[Statement (programming)|statements]], usually without '[[goto (command)|goto]]' commands.

<source lang="pascal">
while a <> b do  WriteLn('Waiting');

if a > b then WriteLn('Condition met')   {no semicolon allowed!}
           else WriteLn('Condition not met');

for i := 1 to 10 do  {no semicolon for single statements allowed!}
  WriteLn('Iteration: ', i);

repeat
  a := a + 1
until a = 10;

case i of
  0 : Write('zero');
  1 : Write('one');
  2 : Write('two');
  3,4,5,6,7,8,9,10: Write('?')
end;
</source>

===Procedures and functions===
Pascal structures programs into procedures and functions.

<source lang="pascal">
program Printing;

var i : integer;

procedure Print(j : integer);
begin
  ...
end;

begin { main program }
  ...
  Print(i);
end.
</source>
Procedures and functions can nest to any depth, and the 'program' construct is the logical outermost block.

Each procedure or function can have its own declarations of goto labels, constants, types, variables, and other procedures and functions, which must all be in that order.
This ordering requirement was originally intended to allow efficient [[single-pass compilation]]. However, in some dialects (such as [[Embarcadero Delphi]]) the strict ordering requirement of declaration sections has been relaxed.

===Semicolons as statement separators===
Pascal adopted many language syntax features from the [[ALGOL]] language, including the use of a semicolon as a statement separator.  This is in contrast to other languages, such as [[PL/I]], [[C (programming language)|C]] etc. which use the semicolon as a statement terminator.  As illustrated in the above examples, no semicolon is needed before the '''<tt>end</tt>''' keyword of a record type declaration, a block, or a ''case'' statement; before the '''<tt>until</tt>''' keyword of a repeat statement; and before the '''<tt>else</tt>''' keyword of an ''if'' statement.

The presence of an extra semicolon was not permitted in early versions of Pascal.  However, the addition of [[ALGOL]]-like empty statements in the 1973 ''Revised Report'' and later changes to the language in ISO 7185:1983 now allow for optional semicolons in most of these cases.  A semicolon is still not permitted immediately before the ''<tt>else</tt>'' keyword in an ''if'' statement, because the <tt>else</tt> follows a single statement, not a statement sequence. In the case of nested ifs, a semicolon cannot be used to avoid the [[dangling else]] problem (where the inner if does not have an else, but the outer if does) by putatively terminating the nested if with a semicolon – this instead terminates both if clauses. Instead, an explicit <code>begin...end</code> block must be used.<ref>''Pascal,'' Nell Dale and Chip Weems, "Dangling Else", [https://books.google.com/books?id=5x2k4vWwn1wC&pg=PA160 p. 160–161]</ref>

Programmers usually include these extra semicolons out of habit and to avoid changing the last line of a statement sequence when new code is appended.

==Resources==

===Compilers and interpreters===
Several Pascal compilers and interpreters are available for general use:

* [[Embarcadero Delphi|Delphi]] is Embarcadero's (formerly Borland/CodeGear) flagship [[rapid application development]] (RAD) product. It uses the Object Pascal language (termed 'Delphi' by Borland), descended from Pascal, to create applications for [[Microsoft Windows|Windows]], [[macOS]], [[iOS]], and [[Android (operating system)|Android]]. The .NET support that existed from D8 through D2005, D2006 and D2007 has been terminated, and replaced by a new language (Prism, which is rebranded Oxygene, see below) that is not fully backward compatible. In recent years [[Unicode]] support and generics were added (D2009, D2010, Delphi XE).
* [[Free Pascal]] is a multi-platform compiler written in [[Object Pascal]] (and is [[self-hosting]]).  It is aimed at providing a convenient and powerful compiler, both able to compile legacy applications and to be the means of developing new ones. It is distributed under the [[GNU GPL]], while packages and runtime library come under a modified [[GNU Lesser General Public License|GNU LGPL]]. Apart from compatibility modes for [[Turbo Pascal]], Delphi and Mac Pascal, it also has its own procedural and object-oriented syntax modes with support for extended features such as [[Operator (programming)|operator]] overloading.  It supports many platforms and operating systems.  Current versions also feature an ISO mode.
* [[ModernPascal|Modern Pascal]] is a multi-platform interpreter and p-code compiler written in [[Free Pascal]].  It is aimed at providing alternative solutions for PHP and node.js, using either an ISO standard pascal dialect or a hybrid supporting JavaScript/C operators. From the CLI it is useful as a Free Pascal interpreter.
* [[Turbo51]] is a free Pascal compiler for the [[Intel 8051|8051 family]] of microcontrollers, with [[Turbo Pascal]]&nbsp;7 syntax.
* [[Oxygene (programming language)|Oxygene]] (formerly known as ''Chrome'') is an Object Pascal compiler for the [[.NET Framework|.NET]] and [[Mono (software)|Mono]] platforms.  It was created and is sold by [http://www.remobjects.com/ RemObjects Software], and sold for a while by Embarcadero as the backend compiler of [[Delphi Prism|Prism]].
* [[Kylix (software)|Kylix]] was a descendant of [[Object Pascal|Delphi]], with support for the [[Linux]] operating system and an improved object library.  It is no longer supported.  Compiler and IDE are available now for non-commercial use.
* [[GNU Pascal]] Compiler (GPC) is the Pascal compiler of the [[GNU Compiler Collection]] (GCC).  The compiler itself is written in C, the runtime library mostly in Pascal.  Distributed under the [[GNU General Public License]], it runs on many platforms and operating systems.  It supports the ANSI/ISO standard languages and has partial Turbo Pascal dialect support.  One of the more painful omissions is the absence of a 100% Turbo Pascal-compatible (short)string type.  Support for Borland Delphi and other language variations is quite limited. There is some support for Mac-pascal however.
* [http://code.google.com/p/dwscript/ DWScript] aka DelphiWebScript, is an interpreter created by Matthias Ackermann and Hannes Hernler in 2000. Current version runs a dialect of Object Pascal largely compatible with Delphi, but also supports language constructs elements introduced in Prism. DWScript code can be embedded into Delphi applications similar to PascalScript, compiled into standalone application using SimpleMobileStudio or compiled into JavaScript code and placed on a web page.<ref>{{cite web|url=https://code.google.com/p/dwscript/downloads/detail?name=Flock-JSCodeGenDemo.7z&can=2&q=|title=Flock-JSCodeGenDemo.7z -   dwscript -    "Flock" DWScript / JavaScript CodeGen demo -   Delphi Web Script general purpose scripting engine - Google Project Hosting|publisher=|accessdate=11 August 2015}}</ref>
* [http://www.visible-software.com/prod-dp.html Dr. Pascal] is an interpreter that runs Standard Pascal.  Notable are the "visible execution" mode that shows a running program and its variables, and the extensive runtime error checking.  Runs programs but does not emit a separate executable binary.  Runs on DOS, Windows in DOS window, and old Macintosh.
* [http://www.visible-software.com/prod-ep.html Dr. Pascal's Extended Pascal Compiler] tested on DOS, Windows 3.1, 95, 98, NT.
* [[Virtual Pascal]] was created by Vitaly Miryanov in 1995 as a native OS/2 compiler compatible with Borland Pascal syntax.  Then, it had been commercially developed by fPrint, adding Win32 support, and in 2000 it became freeware.  Today it can compile for Win32, OS/2 and Linux, and is mostly compatible with Borland Pascal and Delphi.  Development was canceled on April 4, 2005.
* [http://homepages.cwi.nl/~steven/pascal/ P4 compiler], the basis for many subsequent Pascal-implemented-in-Pascal compilers. It implements a subset of full Pascal.
* [http://www.standardpascal.com/p5.html P5 compiler], is an ISO 7185 (full Pascal) adaption of P4.
* [http://smartmobilestudio.com Smart Mobile Studio] is a Pascal to HTML5/Javascript compiler
* [[Turbo Pascal]] was the dominant Pascal compiler for PCs during the 1980s and early 1990s, popular both because of its powerful extensions and extremely short compilation times. Turbo Pascal was compactly written and could compile, run, and debug all from memory without accessing disk.  Slow floppy disk drives were common for programmers at the time, further magnifying Turbo Pascal's speed advantage.  Currently, older versions of Turbo Pascal (up to 5.5) are available for free download from Borland's site.
* [http://www.moorecad.com/ippas/ IP Pascal] Implements the language "Pascaline" (named after [[Pascal's calculator]]), which is a highly extended Pascal compatible with original Pascal according to ISO 7185. It features modules with namespace control, including parallel tasking modules with semaphores, objects, dynamic arrays of any dimensions that are allocated at runtime, overloads, overrides, and many other extensions. IP Pascal has a built-in portability library that is custom tailored to the Pascal language. For example, a standard text output application from 1970's original Pascal can be recompiled to work in a window and even have graphical constructs added.
* [http://ts.fujitsu.com/products/bs2000/software/compiler/pascalxt.html Pascal-XT] was created by [[Siemens]] for their [[mainframe computer|mainframe]] operating systems [[BS2000]] and [[SINIX]].
* [[PocketStudio]] is a Pascal subset compiler and RAD tool for [[Palm OS]] and MC68xxx processors with some own extensions to assist interfacing with the Palm OS API. It resembles Delphi and Lazarus with a visual form designer, an object inspector and a [[source code editor]].
* [[MIDletPascal]] – A Pascal compiler and IDE that generates small and fast Java bytecode specifically designed to create software for mobiles
* [http://www.dcs.gla.ac.uk/~wpc/reports/compilers/compilerindex/Doc2.html Vector Pascal] Vector Pascal is a language for [[SIMD]] instruction sets such as the MMX and the AMD 3d Now, supporting all Intel and AMD processors, and Sony's PlayStation 2 Emotion Engine.
* [http://www.morfik.com Morfik Pascal] allows the development of Web applications entirely written in Object Pascal (both server and browser side).
* [http://www.wdsibyl.org WDSibyl] – Visual Development Environment and Pascal compiler for Win32 and OS/2
* [http://www.ppcompiler.org PP Compiler, a compiler for Palm OS that runs directly on the handheld computer.]
* [http://www.standardpascal.org/CDC6000pascal.html CDC 6000 Pascal compiler] is the source code for the first (CDC 6000) Pascal compiler.
* {{anchor|Pascal-S}}[http://www.moorecad.com/standardpascal/pascals.html Pascal-S]<ref>"Pascal-S: A Subset and Its Implementation", N. Wirth in Pascal – The Language and Its Implementation, by D.W. Barron, Wiley 1979.</ref>
* [http://aminet.net/package/dev/lang/AmigaPascal AmigaPascal] is a free Pascal compiler for the Amiga computer.

A very extensive list can be found on [http://pascaland.org Pascaland]. The site is in French, but it is basically a list with URLs to compilers; there is little barrier for non-Francophones. The site, [http://pascal-central.com Pascal Central], a Mac centric Pascal info and advocacy site with a rich collection of article archives, plus links to many compilers and tutorials, may also be of interest.

===IDEs===
* [[Dev-Pascal]] is a Pascal [[integrated development environment|IDE]] that was designed in Borland [[Object Pascal|Delphi]] and which supports Free Pascal and GNU Pascal as backends.
* [[Lazarus (software)|Lazarus]] is a free Delphi-like visual cross-platform IDE for [[rapid application development]] (RAD). Based on [[Free Pascal]], Lazarus is available for numerous platforms including [[Linux]], [[FreeBSD]], [[macOS]] and [[Microsoft Windows]].

===Libraries===
*[http://wol.sourceforge.net WOL Library] for creating GUI applications with the Free Pascal Compiler.

==Standards==

===ISO/IEC 7185:1990 Pascal===
In 1983, the language was standardized, in the international standard IEC/ISO 7185,<ref>{{cite book|title=ISO/IEC 7185:1990 Pascal|url=http://www.pascal-central.com/docs/iso7185.pdf|accessdate=16 September 2014}}</ref> and several local country specific standards, including the American ANSI/IEEE770X3.97-1983, and ISO 7185:1983. These two standards differed only in that the ISO standard included a "level 1" extension for conformant arrays (an array where the boundaries of the array are not known until run time), where ANSI did not allow for this extension to the original (Wirth version) language. In 1989, ISO 7185 was revised (ISO 7185:1990) to correct various errors and ambiguities found in the original document.

The ISO 7185 was stated to be a clarification of Wirth's 1974 language as detailed by the User Manual and Report [Jensen and Wirth], but was also notable for adding "Conformant Array Parameters" as a level 1 to the standard, level 0 being Pascal without conformant arrays. This addition was made at the request of [[C. A. R. Hoare]], and with the approval of Niklaus Wirth. The precipitating cause was that Hoare wanted to create a Pascal version of the [[NAG Numerical Libraries|(NAG) Numerical Algorithms Library]], which had originally been written in FORTRAN, and found that it was not possible to do so without an extension that would allow array parameters of varying size. Similar considerations motivated the inclusion in ISO 7185 of the facility to specify the parameter types of procedural and functional parameters.

Note that Niklaus Wirth himself referred to the 1974 language as "the Standard", for example, to differentiate it from the machine specific features of the [[CDC 6000]] compiler. This language was documented in ''The Pascal Report'',<ref>{{cite book|last1=Wirth|first1=Niklaus|title=The Programming Language Pascal (Revised Report)|date=July 1973|publisher=ETH Zürich|url=http://www.standardpascal.com/The_Programming_Language_Pascal_1973.pdf|accessdate=16 September 2014}}</ref> the second part of the "Pascal users manual and report".

On the large machines (mainframes and minicomputers) Pascal originated on, the standards were generally followed. On the [[IBM Personal Computer|IBM PC]], they were not. On IBM&nbsp;PCs, the Borland standards Turbo Pascal and Delphi have the greatest number of users. Thus, it is typically important to understand whether a particular implementation corresponds to the original Pascal language, or a Borland dialect of it.

The IBM&nbsp;PC versions of the language began to differ with the advent of UCSD Pascal, an interpreted implementation that featured several extensions to the language, along with several omissions and changes. Many UCSD language features survive today, including in Borland's dialect.

===ISO/IEC 10206:1990 Extended Pascal===
In 1990, an extended Pascal standard was created as ISO/IEC 10206,<ref>{{cite book|title=Extended Pascal: ISO/IEC 10206:1990|url=http://www.dcs.gla.ac.uk/~wpc/reports/compilers/compilerindex/iso10206.ps|accessdate=16 September 2014}}</ref> which is identical in technical content<ref name="ISO/ANSI identical">{{cite web|title=Language standards: Pascal, Extended Pascal, Fortan|url=http://www.prosperosoftware.com/std.html|accessdate=16 September 2014|ref=identical|archive-url=https://web.archive.org/web/20140714024231/http://www.prosperosoftware.com/std.html|archive-date=2014-07-14}}</ref> to IEEE/ANSI 770X3.160-1989<ref>{{cite book|title=770X3.160-1989 - IEEE/ANSI Standard for the Programming Language Extended Pascal|url=https://dx.doi.org/10.1109/IEEESTD.1990.101061|accessdate=16 September 2014}}</ref>
<!-- WHAT FOLLOW APPEARS FACTUALLY WRONG AND IS COMMENTED OUT FOR FUTURE REFERENCE
In 1993, the ANSI standard was replaced by the ANSI organization with a "pointer" to the ISO 7185:1990 standard, effectively ending its status as a different standard.
-->

===Variations===
Niklaus Wirth's Zurich version of Pascal was issued outside [[ETH Zurich|ETH]] in two basic forms, the CDC 6000 compiler source, and a porting kit called Pascal-P system. The Pascal-P compiler left out several features of the full language. For example, procedures and functions used as parameters, undiscriminated variant records, packing, dispose, interprocedural gotos and other features of the full compiler were omitted.

[[UCSD Pascal]], under Professor [[Kenneth Bowles]], was based on the Pascal-P2 kit, and consequently shared several of the Pascal-P language restrictions. UCSD Pascal was later adopted as Apple Pascal, and continued through several versions there. Although UCSD Pascal actually expanded the subset Pascal in the Pascal-P kit by adding back standard Pascal constructs, it was still not a complete standard installation of Pascal.

In the early 1990s, [[Alan Burns (professor)|Alan Burns]] and [[Geoff Davies (computer scientist)|Geoff Davies]] developed Pascal-FC, an extension to Pl/0 (from the Niklaus' book 'Algorithms+Data Structures=Programs'). Several constructs were added to use Pascal-FC as a teaching tool for Concurrent Programming (such as semaphores, monitors, channels, remote-invocation and resources). To be able to demonstrate concurrency, the compiler output (a kind of [[p-code machine|P-code]]) could then be executed on a virtual machine. This virtual machine not only simulated a normal – fair – environment, but could also simulate extreme conditions (unfair mode).

====Borland-like Pascal compilers====

[[Borland]]'s [[Turbo Pascal]], written by [[Anders Hejlsberg]], was written in assembly language independent of UCSD or the Zurich compilers. However, it adopted much of the same subset and extensions as the UCSD compiler. This is probably because the UCSD system was the most common Pascal system suitable for developing applications on the resource-limited microprocessor systems available at that time.

The [[shrink-wrapped]] Turbo Pascal version 3 and later incarnations, including Borland's [[Object Pascal]] and [[Delphi (programming language)|Delphi]] and non-Borland near-compatibles became popular with programmers including shareware authors, and so the [[Sourceware Archive Group|SWAG]] library of Pascal code features a large amount of code written with such versions as Delphi in mind.

Software products (compilers, and [[Integrated development environment|Interactive]]/[[Rapid Application Development|Rapid]] Development Environments with compilers, in this category:
* [[Turbo Pascal]] - "TURBO.EXE" up to version 7, and Turbo Pascal for Windows ("TPW") and [[Turbo Pascal#Apple Macintosh|Turbo Pascal for Macintosh]].
* [[Turbo Pascal#Windows versions|Borland Pascal 7]] (essentially Turbo Pascal 7 for Windows).
* [[Object Pascal]] - an extension of the Pascal language that was developed at [[Apple Computer]] by a team led by [[Larry Tesler]] in consultation with [[Niklaus Wirth]], the inventor of Pascal; its features were added to Borland's [[Turbo Pascal#Apple Macintosh|Turbo Pascal for Macintosh]] and in 1989 for Turbo Pascal 5.5 for DOS.
* [[Delphi (programming language)|Delphi]] - Object Pascal is essentially its underlying language.
* [[Free Pascal]] (or '''fpc''') - Free Pascal adopted the de facto standard dialect of Pascal programmers, Borland Pascal and, later, Delphi.
* [[PascalABC.NET]] - is a new generation Pascal programming language including [[compiler]] and [[integrated development environment]] (IDE) 
* [[Kylix (software)|Borland Kylix]] is a [[compiler]] and [[integrated development environment]] (IDE) formerly sold by [[Borland]], but later discontinued. It is a [[Linux]] version of the [[Delphi (programming language)|Borland Delphi]] software development environment and [[C++Builder]].
* [[Lazarus (IDE)|Lazarus]] - similar to Kylix in function, is a free cross-platform visual [[integrated development environment]] (IDE) for [[rapid application development]] (RAD) using the [[Free Pascal]] compiler, which supports dialects of [[Object Pascal]], to varying degrees.
* [[Virtual Pascal]] - VP2/1 is a fully Borland Pascal and Borland Delphi compatible 32-bit Pascal compiler for OS/2 and Win 32 (with a Linux version "on the way").<ref>{{cite web|title=Virtual Pascal for OS/2|url=http://www.pascal-central.com/vpascal.html|accessdate=3 April 2016}}</ref>
*  Sybil is an open source Delphi-like IDE and compiler; implementations include [http://www.wdsibyl.org WDSibyl] for [[Microsoft Windows]] and [[OS/2]], a commercial [[Borland Pascal]] compatible environment released by a company called Speedsoft that was later developed into a Delphi like [[Rapid application development|RAD]] environment called Sybil and then open sourced under the GPL when that company closed down; [[Open Sybil]] is an ongoing project, an [[Open source]] Pascal RAD (Rapid Application Development) Tool for OS/2 and eCS that was originally based on Speedsoft's WDsybl SPCC (Sibyl Portable Component Classes) and SVDE (Sibyl Visual Development Tool) sources but now the core is [[IBM System Object Model|SOM]], WPS and [[OpenDoc]].<ref>{{cite web|title=netlabs.org -  Project: Open Sibyl|url=http://sibyl.netlabs.org/en/site/index.xml|accessdate=3 April 2016}}</ref>

===List of related standards===
* [[International Organization for Standardization|ISO]] 8651-2:1988 ''Information processing systems – Computer graphics – Graphical Kernel System (GKS) language bindings – Part 2: Pascal''

==Reception==
Pascal generated a wide variety of responses in the computing community, both critical and complimentary.

===Early criticism===
While very popular in the 1980s and early 1990s, implementations of Pascal that closely followed Wirth's initial definition of the language were widely criticized for being unsuitable for use outside teaching. [[Brian Kernighan]], who popularized the [[C (programming language)|C language]], outlined his most notable criticisms of Pascal as early as 1981, in his paper ''Why Pascal Is Not My Favorite Programming Language''.<ref>Brian W. Kernighan (1981). [http://www.lysator.liu.se/c/bwk-on-pascal.html Why Pascal is Not My Favorite Programming Language]</ref> The most serious problem described in his article was that array sizes and string lengths were part of the type, so it was not possible to write a function that would accept variable length arrays or even strings as parameters. This made it unfeasible to write, for example, a sorting library. The author also criticized the unpredictable order of evaluation of boolean expressions, poor library support, and lack of [[static variable]]s, and raised a number of smaller issues. Also, he stated that the language did not provide any simple constructs to "escape" (knowingly and forcibly ignore) restrictions and limitations.  More general complaints from other sources<ref name="Hoare.Sneeringer.Welsh.1977"/><ref>O. Lecarme, P. Desjardins, "More Comments on the Programming Language Pascal," ''Acta Informatica 4'', pp. 231–243 (1975)</ref> noted that the scope of declarations was not clearly defined in the original language definition, which sometimes had serious consequences when using [[forward declaration]]s to define pointer types, or when record declarations led to [[Recursive data type|mutual recursion]], or when an identifier may or may not have been used in an enumeration list. Another difficulty was that, like [[ALGOL 60]], the language did not allow procedures or functions passed as parameters to predefine the expected type of their parameters.

Most of Kernighan's criticisms were directly addressed in the paper "The Pascal Programming Language",<ref>[http://pascal-central.com/ppl/index.html The Pascal Programming Language]</ref> specifically, under Myth 6: Pascal is Not For Serious Programmers.<ref>[http://pascal-central.com/ppl/chapter4.html#Myths Pascal Myths]</ref>

Despite initial criticisms, Pascal continued to evolve, and most of Kernighan's points do not apply to versions of the language which were enhanced to be suitable for commercial product development, such as Borland's [[Turbo Pascal]].  As Kernighan predicted in his article, most of the extensions to fix these issues were incompatible from compiler to compiler.  Since the early 1990s, however, most of the varieties seem condensed into two categories, ISO and Borland-like.

Extended Pascal addresses many of these early criticisms.  It supports variable-length strings, variable initialization, separate compilation, short-circuit boolean operators, and default (OTHERWISE) clauses for case statements.<ref>[http://pascal-central.com/ppl/chapter3.html#Extended Extended Pascal]</ref>

==See also==
* [[Concurrent Pascal]]
* [[Comparison of Pascal and Borland Delphi]]
* [[Comparison of Pascal and C]]
* [[Modula-2]]
* [[Oberon (programming language)]]
* [[Object Pascal]]
* [[Real Programmers Don't Use Pascal]]

==References==
{{Reflist|30em}}

==Further reading==
* Niklaus Wirth: ''The Programming Language Pascal.'' 35–63, Acta Informatica, Volume 1, 1971.
* C. A. R. Hoare: ''Notes on data structuring.'' In O-J Dahl, E W Dijkstra and C A R Hoare, editors, Structured Programming, pages 83–174. Academic Press, 1972.
* C. A. R. Hoare, Niklaus Wirth: ''An Axiomatic Definition of the Programming Language Pascal.'' 335–355, Acta Informatica, Volume 2, 1973.
* [[Kathleen Jensen]] and Niklaus Wirth: ''[http://www.cs.inf.ethz.ch/~wirth/books/Pascal/ PASCAL – User Manual and Report].'' Springer-Verlag, 1974, 1985, 1991, {{ISBN|0-387-97649-3}} and {{ISBN|3-540-97649-3}}.
* Niklaus Wirth: ''[[Algorithms + Data Structures = Programs]]''. Prentice-Hall, 1975, {{ISBN|0-13-022418-9}}.
* Niklaus Wirth: ''An assessment of the programming language PASCAL''. 23–30 ACM SIGPLAN Notices Volume 10, Issue 6, June 1975.
* N. Wirth, and A. I. Wasserman, ed: ''Programming Language Design.'' IEEE Computer Society Press, 1980
* D. W. Barron (Ed.): ''Pascal – The Language and its Implementation.'' John Wiley 1981, {{ISBN|0-471-27835-1}}
* Peter Grogono: ''Programming in Pascal'', Revised Edition, Addison-Wesley, 1980
* Richard S. Forsyth: ''Pascal in Work and Play'', Chapman and Hall, 1982
* N. Wirth, M. Broy, ed, and E. Denert, ed: [http://www.swissdelphicenter.ch/en/niklauswirth.php ''Pascal and its Successors''] in ''Software Pioneers: Contributions to Software Engineering.'' Springer-Verlag, 2002, {{ISBN|3-540-43081-4}}
* N. Wirth: [http://portal.acm.org/citation.cfm?id=155378 ''Recollections about the Development of Pascal.''] ACM SIGPLAN Notices, Volume 28, No 3, March 1993.

==External links==
{{Commons category}}
{{Wikibooks|Pascal}}
* [http://pascal-central.com/ppl/index.html The Pascal Programming Language]
* [http://www.standardpascal.org Standard Pascal] – resources and history of original, standard Pascal
* [http://wiki.lazarus.freepascal.org/Portal:SciTech Free Pascal SciTech portal] – with applications of Lazarus and Free Pascal for Science, medicine and technology
* [http://www.standardpascal.com/PascalP.html Pascal-P] – the Pascal-P compiler and versions
* [http://www.standardpascal.com/p5.html Pascal-P5] – Pascal-P5 web page
* [https://sourceforge.net/projects/pascalp5/ Pascal-P5 source code] – SourceForge project for P5
* [https://vintagebigblue.org/Compilerator/PASCAL8K/pascal8kCompile.php Online Vintage Pascal8000 Compiler] – for small experiments

{{Programming languages}}
{{Pascal programming language family|state=uncollapsed}}
{{ISO standards}}

{{Authority control}}

[[Category:Academic programming languages]]
[[Category:Articles with example Pascal code]]
[[Category:Educational programming languages]]
[[Category:Pascal (programming language)| ]]
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[[Category:Programming languages created in 1970]]
[[Category:Programming languages with an ISO standard]]