Borland Delphi

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Borland Delphi is an implementation of the Pascal programming language developed and sold by CodeGear (originally Borland) for Microsoft Windows. It is an Integrated Development Environment (IDE) with editor, compiler, linker, and debugger. Like Visual BASIC, Delphi is a Rapid Application Development (RAD) environment. Delphi is the successor to Borland Pascal and Turbo Pascal. The Pascal language has been extended, including support for huge strings with a theoretical maximum size of 2 Gb (version 2 and later only). It uses the Visual Control Library (VCL) as an abstraction to the Microsoft Windows API.

Basic concepts

Delphi programs are compiled from a number of source files, the main ones being units and forms. A unit is a text file, with a .pas extension, that contains Delphi code, organised into interface and implementation sections.

The interface section contains declarations that can, for the most part, be referred to by other units. These declarations include constants, variables, "types" and headers of procedures and functions. "Types" include classes (objects) and sets.

The implementation section contains code for each of the procedures and functions, including the methods of objects, that are in the interface section, or other procedures and functions declared in the implementation section. These latter procedures and functions are not "visible" to other units.

Units can also list other units so that code within the units can call code contained in other units (if it is declared in the other units' interface section).

A form is an encapsulation of a Windows window, on which various controls can be placed when designing the program. The design of each form is contained in a text or binary file with a .dfm extension. The form is declared as an object (class) in an accompanying unit that is also created. Code associated with that form is written in the unit associated with that form.


Although the core code is highly compatible with the earlier Borland Pascal and Turbo Pascal products, Windows-specific parts of Delphi are incompatible with previous Pascal products from Borland that used Object Windows Library (OWL). Other incompatibilities related to proprietary function libraries also caused upgrade problems. Nevertheless, VCL is much improved over OWL.

Because of the managed code environment, .NET applications introduced some incompatibilities with non-.NET code.

Release History

Version Date Comments
Version 1 February 14 1995 Produced 16-bit code
Version 2 February 10 1996 Introduced 32-bit code
Version 3 August 5 1997
Version 4 June 17 1998
Version 5 August 10, 1999
Version 6 May 21 2001
Version 7 August 9 2002
Version 8 December 22, 2003 Introduced .NET applications
Version 2005 August 12 2004
Version 2006 August 10 2005
Version 2007 March 19 2007

Versions 8 onwards have included the ability to generate either .NET or traditional Windows applications from the same source code (as long as some restrictions are observed), providing a migration path for developers wanting to market their products to users of both environments.