In computing, 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 popularity of VCL comes from its tight integration with visual RAD tools from Borland.
A cross-platform equivalent of 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 VCL.
As an object-oriented approach, the VCL forms an object hierarchy where all other objects inherit or indirectly inherit the TObject class. This is necessary as Delphi does not support multiple inheritance, unlike C++. The VCL approach is common because it was used by Smalltalk, the first true object-oriented programming language. This approach is shared by the Java programming language, which has a base class called Object.