Introducing the Visual Component Library (VCL)
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RAD Studio offers a powerful Integrated Development Environment that makes building native Windows applications extremely easy. The Visual Component Library (also known as VCL) offers a large number of visual and nonvisual controls and components that can be used to build almost any desired user interface. Besides the VCL, RAD Studio provides an extensive library of routines and classes, called the Run Time Library (known as RTL), which provides the common functionality needed in all applications. The separation between the RTL and the VCL in RAD Studio is that the RTL is implemented in the System unit scope, whereas the VCL is implemented in the Vcl unit scope. However, most of the documentation refers to the VCL-RTL as simply VCL.
The most important benefits of the VCL over other competing technologies are as follows:
- A standard set of components that includes all controls provided by the Windows UI framework. This set consists of components such as buttons, edits, menus, and so on. The VCL also extends some of these controls, offering you even more functionality than is normally provided by the Windows controls.
- An extended set of components not normally present in the Windows UI framework. These components are built on top of the standard set.
- Actions, a key concept extensively used in VCL applications, allow you to centralize all the interaction logic of your user interface.
- A number of data-aware controls that can be linked to a data source at design time. These components are widely used in database applications.
- Ribbon controls that allow you to build the next generation of user interfaces that integrate nicely with the Windows Vista and Microsoft Office 2007 look-and-feel. See How To Build an Application that Uses Ribbon Controls.
- DBExpress and dbGo database frameworks. These frameworks can be used with all the data-aware controls, simplifying your application development more than ever. See Developing Database Applications.
- Internet Direct, also known as Indy, that provides an extensive number of components used in Internet-connected applications. Indy includes client and server components for today’s most used communication protocols on the Internet.
- DataSnap, which allows you to build distributed applications. See Creating Multi-Tiered Applications Index.
- Easy integration of any exposed OLE and ActiveX objects in your application. RAD Studio provides a set of tools that allow creating a wrapper component over any public ActiveX. This wrapper component can be used as any normal VCL component inside your application. See Developing COM-based Applications.
Even though this is not the full list of components available in the VCL, the components mentioned earlier are the most widely used and appreciated VCL components. To see all available components, check out the Tool Palette in RAD Studio.