Visual Component Library

VCL (Visual Component Library) is a visual component-based framework for developing Microsoft Windows applications, developed by Borland for use in its Delphi and C++ Builder software development environment. It is written in Object Pascal.

Much of the popularity of the VCL comes from its tight integration with visual RAD tools from Borland.

A cross-platform equivalent of the VCL called CLX (Component Library for Cross Platform) was later developed for use in Delphi, C++ Builder and Kylix, it was however abandoned in favor of the VCL.

As an object-oriented approach, the VCL forms an object hierarchy where all other objects inherit or indirectly inherit the TObject class (thus, TObject is a superclass). This is a common approach shared by the Java programming language, Smalltalk, and many other object-oriented programming languages.

VCL components cover Windows controls like windows (TForm class), controls (e.g., TButton, TCheckBox, TLabel classes) as well as database access (e.g., ADO or IBX components) or Internet connections (Indy components). The component approach allows programmers to extend the VCL with many visual and non-visual additional components. The best known component packages are JEDI or TMS.

While not all VCL components are thread-safe, VCL supports multi-threading too.

VCL provides native support for PME (Properties Methods Events) model at .NET level and fully complies with Object Oriented Design (i.e.: polymorphism, implementation inheritance, and encapsulation). Partial ports of VCL for C++ exist as well (BCB product line). LCL is an open source port of VCL (see Lazarus) currently ported to over 20 hardware and software platforms.

See also

* Delphi
* CLX
* Object Windows Library
* Turbo Vision
* Software component
* C++ Builder
* Delphi for PHP

External links

* [JEDI Visual Component Library] (JVCL) and [http://homepages.borland.com/jedi/jcl/ JEDI Code Library] (JCL) - huge open source collection of components based on VCL
* [http://www.codepedia.com/1/CppVcl CodePedia C++ VCL page] (no Pascal page yet)