View source for Pascal

{{for|the mathematician|Blaise Pascal}}
{{for|the unit of pressure|Pascal (unit)}}{{Unreferenced|date=August 2025}}
'''Pascal''' is a [[programming language]].
It was created in [[1970]] by [[Niklaus Wirth]], to help people learn how to make computer programs.
== Development ==
Now, there are many different dialects of the language, some of which support [[object-oriented programming]].
In 1990 the “Pascal” and “Extended Pascal” standards were registered with the [[International Organization for Standardization]].
== Description ==
Every [[Variable#Variables in computer science|variable]] has to be declared before it is used.
Pascal is a strongly typed programming language:
Every variable has a [[data type]].
You are only allowed to assign values to the variable that are valid for the data type.
This ensures that the programmer does not make unintentional mistakes.

Pascal is a [[imperative programming|imperative language]].
The language distinguishes between procedures and [[function]]s.
A <syntaxhighlight lang="pascal" inline>function</syntaxhighlight> returns a value, a <syntaxhighlight lang="pascal" inline>procedure</syntaxhighlight> does not.
As such, a <syntaxhighlight lang="pascal" inline>function</syntaxhighlight> call appears in an expression, whereas a <syntaxhighlight lang="pascal" inline>procedure</syntaxhighlight> invocation is a statement.
== Code samples ==
This code prints [[Hello world program|<syntaxhighlight lang="text" inline>Hello world!</syntaxhighlight>]] at console window:
<syntaxhighlight lang="pascal" line="1">
program helloWorld(output);
begin
	writeLn('Hello world!');
	{ which is short for: writeLn(output, 'Hello world!); }
end.
</syntaxhighlight>

This code calculate [[factorial]] of a positive integer, using [[recursion]].
<syntaxhighlight lang="pascal" line="1">
program factorialDemo(input, output);

function factorial(n: integer): integer;
begin
	if n < 2 then
	begin
		{ the result of a function is stored in a variable }
		{ that has the same name as the function: }
		factorial := 1;
	end
	else
	begin
		factorial := n * factorial(n - 1);
	end
end;

var
	n: integer;
begin
	write('Enter number: ');
	readLn(n);
	writeLn(factorial(n));
end.
</syntaxhighlight>
== Pascal variants ==
* [https://www.gnu-pascal.de/ GNU Pascal]
* [[Object Pascal]]
* [https://www.freepascal.org Free Pascal]
* [[Delphi programming language|Delphi]] – Modern [[IDE]] for creating GUI programs for [[Microsoft Windows]]. There is an [[open source]] clone of it for [[Microsoft Windows|Windows]], [[Mac OS X]] and [[FreeBSD]], named [[Lazarus(IDE)|Lazarus]].
* [[Turbo Pascal]]

{{Tech-stub}}
{{authority control}}
[[Category:Programming languages]]