Lazarus is a free open source visual integrated development environment (IDE) built upon the Free Pascal programming language and compiler. With Lazarus you can design efficient desktop applications using a single base of program code and targeting many different computer operating systems and processor architectures. Lazarus provides a large set of rapid application development (RAD) tools and includes an extensive object oriented class library known as the Lazarus component library (LCL).

The LCL encapsulates functionality, components, and visual controls common across all desktop platforms. These include, but are not limited to, concepts such as the visual design of forms, buttons, menus, dialogs, data connections, and graphic canvases. This guide will introduce you to the Lazarus IDE and detail how to use it along with the LCL to develop general-purpose, database, and Internet enabled desktop applications.

If you intend to work through the examples presented in this guide, or desire to follow along with a hands on approach to learning Free Pascal, we strongly recommend that you use one of our setup bundles to get started. The setup programs will install both Free Pascal and Lazarus on your system and they are specifically designed to not interfere with any other development tools you many already have on your computers.

Style conventions in all guides are organized as follows. Inline snippets of Pascal source code are presented in a white box with a monospaced font like so:

Blocks or multiple lines of Pascal code are presented in monospaced font using syntax highlighting and lines numbers like so:

procedure TForm1.Button1(Sender: TObject);
begin
  ShowMessage('Hello World');
end;

The following topics are covered in this guide: