Object Pascal refers to a branch of object-oriented derivatives of Pascal, mostly known as the primary programming language of CodeGear Delphi. Pascal compilers, including those for Object Pascal, generally runs extremely fast while producing highly optimized code.

Borland used the name "Object Pascal" for the programming language in the first versions of Delphi, but later renamed it to the "Delphi programming language". However, compilers that claim to be Object Pascal compatible are often trying to be compatible with Delphi source code.

CodeGear sells integrated development environments (IDEs) that compile the Delphi programming language to Microsoft Windows, the Microsoft .NET Framework and Linux. The open source Free Pascal project allows the language to be compiled for a range of operating systems including Linux, Mac OS/Mac OS X, Win32, Win64, Windows CE, and for several different hardware architectures. Also, a free compiler, Turbo51, is available for producing code for Intel 8051 chips.

Today, Object Pascal is used collectively to refer to different dialects of the Pascal language with object-oriented programming extension, although these dialects are mostly compatible with CodeGear's implementation.

Early history at Apple

Object Pascal is an extension of the Pascal programming language that was developed at Apple Computer by a team led by Larry Tesler in consultation with Niklaus Wirth, the inventor of Pascal. It is descended from an earlier object-oriented version of Pascal called Clascal, which was available on the Lisa computer.

Object Pascal was needed in order to support MacApp, an expandable Macintosh application framework that would now be called a class library. Object Pascal extensions and MacApp itself were developed by Barry Haynes, Ken Doyle, and Larry Rosenstein, and were tested by Dan Allen. Larry Tesler oversaw the project, which began very early in 1985 and became a product in 1986.

Apple dropped support for Object Pascal when they moved from Motorola 68K chips to IBM's PowerPC architecture in 1994.

An Object Pascal extension was also implemented in the Think Pascal IDE. The IDE includes the compiler and an editor with Syntax highlighting and checking, a powerful debugger and a class library. Many developers preferred Think Pascal instead of MacApp because it offered a tight integration of its tools. The development stopped after the 4.01 version because the company was bought by Symantec. The developers then left the project.

The Borland and CodeGear years

In 1986, Borland introduced similar extensions, also called Object Pascal, to the Turbo Pascal product for the Macintosh, and in 1989 for Turbo Pascal 5.5 for DOS.

When Borland refocused from MS-DOS to Windows in 1994, they created a successor to Turbo Pascal, called Delphi and introduced a new set of extensions to create what is now known as the Delphi language.

The development of Delphi started in 1993 and Delphi 1.0 was officially released in the United States on 14 February 1995. While code using the Turbo Pascal object model could still be compiled, Delphi featured a new syntax using the keyword class in preference to object, the Create constructor and a virtual Destroy destructor (and negating having to call the New and Dispose procedures), properties, method pointers, and some other things. These were inspired by the ISO working draft for object-oriented extensions, but many of the differences to Turbo Pascal's dialect (such as the draft's requirement that all methods be virtual) were ignored.

The Delphi language continued to evolve throughout the years to support new language concepts such as 64-bit integers and dynamic arrays.

Compilers

There are many compilers that are mostly compatible with the Object Pascal language from Delphi. Many of these were created to enable Object Pascal compilation on different platforms and under various licenses.

• CodeGear Delphi is probably the best known compiler. It targets Win16, Win32 and the .NET 1.x, 2.0.
• Borland Kylix is a Linux variant of Delphi which only targets Intel 32-bit Linux using Qt. It is no longer updated. Modern distributions often do not work out-of-the box with it.
• Free Pascal is a command-line compiler aimed at source compatibility with the core feature set of both the Turbo Pascal and the Delphi dialects. The current version, 2.2, is highly Delphi6/7 compatible. FPC generates code for x86, x86-64, PowerPC, SPARC and ARM processors under various operating systems, including Win32, Win64, Linux, FreeBSD, Mac OS and Mac OS X (including an Xcode integration kit). Beyond command-line usage, several development environments are available for Free Pascal, in particular the Lazarus IDE.
• GNU Pascal (A separately-distributed part of the GNU Compiler Collection) While formally not aimed at the CodeGear dialects of Pascal, it does contain a Borland Pascal compatibility mode, and is very slowly incorporating a few Delphi language features. It is unsuitable for recompiling large bodies of Delphi code directly, but is noteworthy as having prolific support for operating systems and hardware architectures.
• Virtual Pascal is a x86 32-bit Turbo Pascal and Delphi compatible compiler aimed mainly at OS/2 and Windows, although it also developed a DOS+ Extender and an experimental Linux cross-compiler. The compiler’s development stopped at about the level of Delphi V2; its site has been down since 2007, and development of Virtual Pascal has stopped.
• Oxygene (formerly known as Chrome) is an Object Pascal compiler from RemObjects Software that integrates into Microsoft Visual Studio. It is also available as free command-line compiler that runs native on CLI. It targets the .NET and Mono platforms.

Interpreters

Pascal Script (formerly known as InnerFuse) is an open source Object Pascal interpreter/scripting engine written in Delphi. Supports a limited subset of Object Pascal.

Sample "Hello World" programs

Apple's Object Pascal

program ObjectPascalExample;
 
   type
      THelloWorld = object
         procedure Put;
      end;
 
   var
      HelloWorld: THelloWorld;
 
   procedure THelloWorld.Put;
   begin
      WriteLn('Hello, World!');
   end;
 
begin
   New(HelloWorld);
   HelloWorld.Put;
   Dispose(HelloWorld);
end.

Turbo Pascal's Object Pascal

program ObjectPascalExample;
 
   type
      PHelloWorld = ^THelloWorld;
      THelloWorld = object
         procedure Put;
      end;
 
   var
      HelloWorld: PHelloWorld; { this is a pointer to a THelloWorld }
 
   procedure THelloWorld.Put;
   begin
      WriteLn('Hello, World!');
   end;
 
begin
   New(HelloWorld);
   HelloWorld^.Put;
   Dispose(HelloWorld);
end.

Delphi And Free Pascal's Object Pascal

program ObjectPascalExample;
 
type
  THelloWorld = class
    procedure Put;
  end;
 
procedure THelloWorld.Put;
begin
  Writeln('Hello, World!');
end;
 
var
  HelloWorld: THelloWorld;               { this is an implicit pointer }
 
begin
  HelloWorld := THelloWorld.Create;      { constructor returns a pointer }
  HelloWorld.Put;                        { this line dereferences the pointer }
  HelloWorld.Free;
end.

Note that the object construct is still available in Delphi and Free Pascal (Delphi-compatible mode).

Oxygene Object Pascal

namespace ObjectPascalExample;
 
   interface
 
   type
      ConsoleApp = class
         class method Main
      end;
 
      THelloWorld = class
         method Put;
      end;
 
   implementation
 
   method THelloWorld.Put;
   begin
      Console.WriteLine('Hello, World!');
   end;
 
   class method ConsoleApp.Main;
   begin
      var HelloWorld := new THelloWorld;
      HelloWorld.Put;
   end;
 
end.

Development

Many features have been introduced continuously to Object Pascal with extensions to Delphi, now also by Free Pascal. In reaction to criticisms, Free Pascal has adopted generics, and both Delphi and Free Pascal now supports operator overloading (with different grammar, though). Delphi has also introduced many other features since version 7^[1].

See also

• Borland Kylix
• Comparison of programming languages
• Free Pascal
• Hello world program

References

External links

CodeGear

• CodeGear Delphi
• New Language Features In Delphi 2006 and Delphi 2007
• Delphi Wiki
• Torry's Delphi Pages
• Delphi Tutorials
• Russian Delphi Club
• Object Pascal Style Guide

RemObjects Software

• RemObjects Oxygene Homepage
• RemObjects Oxygene Official Wiki
• RemObjects Oxygene Developer Resources, Articles and Videos

Introduction to Object Pascal

• Collection of informative web sites for Delphi beginners
• Discovering Delphi
• MacTech Vol 2 Issue 12 1985

Delphi communities

• Delphi Pages
• Torry's Delphi Pages
• About.com Delphi Programming

Delphi's Object Pascal Language guide

• Delphi 5 "Object Pascal Language Guide"  (PDF, Windows Help)
• Delphi 1.0 Object Pascal Language Reference Guide
• Object Pascal Style Guide

Free Pascal Object Pascal reference guide

• Current version's Object Pascal Ref guide (PDF)
• Current version's Object Pascal Ref guide (html)
• Free Pascal Mac Pascal extensions status page

Tools For Object Pascal

• MSEide+MSEgui
• Lazarus IDE
• Powtils Web Kit

GNU Pascal

• GNU Pascal (GPC) information
• GPC differences to Mac Pascal page

paxCompiler

• Embeddable Pascal compiler