The raw power of Delphi is based on a considerable amount of its Run Time Library functions and procedures. Run Time Library, or VCL routines are functions and procedure that are built into Delphi. This section of About Delphi Programming site provides a through example-reference to the RTL capabilities of Delphi.
In order to run, a Delphi application needs a lot of background information, such as how to interact with the operating system and how to create forms and components, such as buttons and edit boxes. This information is contained in various unit files that are a standard part of Delphi. This collection of units is referred to as the RTL (run time library). The RTL contains a very large number of functions and procedures for you to use.
Browse Delphi's RTL ....
Every routine is presented with a routine header and is described in a few to-the-point words, with sample code plus a link to some "real code" article.
Note 1: If you need help with any Delphi RTL function not (already) explained here, feel free to ask for help!
Note 2: If you are new to Delphi, first read the "Using Delphi's RTL routines" article.