VCl

VCL, or Visual Component Library, is a GUI framework developed by Borland and later Embarcadero for building native Windows applications. It is the primary UI framework used by Delphi and C++Builder, providing a large set of visual and non-visual components that can be dropped onto forms.

Components in VCL include standard controls such as buttons, edits, and lists, as well as more complex controls like grids, trees, and printers, along with data-aware components for database access. The library is organized around an object-oriented class hierarchy with base classes such as TComponent and TControl, supports ownership-based lifetime management, and uses a streaming system to save and load forms from .dfm files.

The programming model is event-driven. Developers write code in Object Pascal or C++ to respond to events such as clicks or key presses. The integrated development environment provides a form designer, a code editor, and debugging tools to support rapid application development.

Platform and language aspects include a design focused on Windows, using the Windows API to render controls and deliver native look and performance. VCL is tightly integrated with the Delphi language and the C++Builder dialect. VCL components are compiled to native code, contributing to fast startup times and responsive user interfaces.

History and status: VCL was introduced with Delphi 1 in the mid-1990s and became the core GUI framework for Windows desktop applications in the Borland/Embarcadero ecosystem. While VCL remains in active use for Windows targets, Embarcadero has also developed FireMonkey (FMX) to support cross-platform development. VCL continues to be a foundational technology in many Delphi and C++Builder projects.

Related topics include the FireMonkey cross-platform framework, Delphi, and C++Builder.