Free Pascal Runtime Library

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The Free Pascal Runtime Library, abbreviated RTL, is Free Pascal's runtime library.

The RTL consists of a collection of units that provide components and classes for general programming tasks. It acts as a basis for Free Pascal's Free Component Library (FCL) and the Lazarus Component Library (LCL). The RTL is licensed under the LGPL with a static linking exception.

Further reading

• Michaël van Canneyt; Florian Klämpfl (2012), Free Pascal (Free Pascal 2 ed.), Computer & Literatur Verlag GmbH, ISBN 978-3936546729, OL 25421359M, 393654672X
• Roderick Person (2013), Getting Started with Lazarus IDE, Packt Publishing, ISBN 978-1782163404, OL 25426631M, 1782163409

External links

• RTL documentation in the Free Pascal Wiki
• Complete online reference

v t e List of widget toolkits
Low-level
On AmigaOS	Intuition
On Classic Mac OS, macOS	Macintosh Toolbox Carbon
On Windows	Windows API UWP WinRT
On Unix, under X11	Xlib XCB X Toolkit Intrinsics
On BeOS, Haiku	BeOS API
Cross-platform	CLI OpenTK C GDK Simple DirectMedia Layer Java JOGL LWJGL
On Android	CLI Xamarin.Android
High-level, platform-specific
On AmigaOS	BOOPSI MUI ReAction GUI Zune
On Classic Mac OS, macOS	Object Pascal MacApp Objective-C, Swift Cocoa Cocoa Touch C++ MacApp PowerPlant THINK C CLI Xamarin.Mac Xamarin.iOS
On Windows	CLI Windows Forms XAML Windows Presentation Foundation Windows UI Library Silverlight Microsoft XNA C++ MFC Active Template Library Windows Template Library Object Windows Library Object Pascal Visual Component Library
On Unix, under X11	Athena (Xaw) LessTif Motif OLIT XForms
On Android	Qt for Android
High-level, cross-platform
C	Enlightenment Foundation Libraries GTK IUP XForms XVT
C++	Bedrock CEGUI Component Library for Cross Platform FLTK FOX toolkit OpenGL User Interface Library gtkmm JUCE Qt Rogue Wave Views TnFOX U++ Wt wxWidgets Simple and Fast Multimedia Library
Objective-C	GNUstep
CLI	Gtk# Tao Framework OpenTK UIML MonoGame Moonlight Xamarin.Forms XWT .NET MAUI
Adobe Flash	Apache Flex MXML
Go	Fyne
Haskell	wxHaskell
Java	Abstract Window Toolkit FXML JavaFX Qt Jambi Swing Standard Widget Toolkit Google Web Toolkit Lightweight User Interface Toolkit
JavaScript	Dojo Toolkit Echo Ext JS Google Closure Tools jQuery UI OpenUI5 Qooxdoo YUI
Common Lisp	CAPI CLIM Common Graphics
Lua	IUP
Pascal	Lazarus Component Library
Object Pascal	Component Library for Cross Platform fpGUI IP Pascal FireMonkey
Perl	Perl/Tk wxPerl
PHP	PHP-GTK wxPHP
Python	Tkinter Kivy PySide PyQt PyGTK wxPython Pyjs
Ruby	Shoes QtRuby
Tcl	Tcl/Tk
XML	GladeXML Lively Kernel Extensible Application Markup Language XUL Wt
shell	Newt CDK Dialog
Dart	Flutter