Object Pascal

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

[edit] Early history at Apple

This section requires expansion with: additional citations.

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 over Apple's implementation of Object Pascal because Think Pascal 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.

[edit] 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.

[edit] Versions

• 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 compatible with Object Pascal are often trying to be compatible with Delphi source code.^{[citation needed]}

• CodeGear, a former subsidiary of Borland and now a part of Embarcadero Technologies, sells integrated development environments (IDE’s) that compile the Object Pascal code to Windows.

• .NET support existed from Delphi 8 through Delphi 2005, Delphi 2006 and Delphi 2007, which now has been replaced by another language, Oxygene (see below), which is not fully backward-compatible.

• The Oxygene programming language developed by RemObjects Software targets the Common Language Infrastructure solely. The Oxygene compiler has been incorporated into a new Delphi development solution owned by Embarcadero, named Delphi Prism, which is Microsoft Visual Studio based.

• The Morfik Pascal programming language developed by Morfik targets the Ajax-enabled Web applications. The Morfik compiler is incorporated into the company's AppsBuilder IDE and allows Object Pascal code to be used in implementing code that will execute both in the browser and on the server. It uses the Free Pascal compiler to generate native binaries from Object Pascal.

• The open source Free Pascal project allows the language to be compiled for a wide range of operating systems—including Linux (32-bit and 64-bit), FreeBSD, Mac OS/Mac OS X, Win32, Win64 and Windows CE—as well as for several different hardware architectures. The first version of Free Pascal for the iPhone SDK 2.x was announced on January 17, 2009.^[1] Now there is also support for embedded (ARM).

• The MIDletPascal is aimed to the Java byte-code platform.

• The open source GNU Pascal compiler is available as a front-end to the GNU compiler collection, which implements the ISO 7185 Pascal standard, and "most" of the ISO 10206 Extended Pascal standard.

• Also, a free compiler, Turbo51, is available for producing code for Intel 8051 chips.

• WDSybil, an open source Delphi like IDE and compiler available for Microsoft Windows and OS/2, originally a commercial Borland Pascal compatible environment released by a company called Speedsoft, that was later developed into a Delphi like RAD called Sybil and then open sourced under the GPL when that company closed down.

[edit] 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 (Delphi 1), Win32 (Delphi 2+) and the .NET 1.x, 2.0 (Delphi 8, Delphi 2005 - 2007).
• 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, 2.4, is highly Delphi 6- or 7-compatible.^{[citation needed]} 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.
• MIDletPascal is a mobile application development tool that generates Java ME bytecode.
• PocketStudio is a Pascal based IDE for Palm OS.

[edit] 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.

[edit] Sample "Hello World" programs

[edit] 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.

[edit] Turbo Pascal's Object Pascal

Still supported in Delphi and Free Pascal. FPC also packages its own substitutes for the libraries/units. Delphi doesn't. The Free Pascal 1.0 series and the FPC textmode IDE are the largest open codebases in this dialect. Free Pascal 2.0 was rewritten in a more Delphi-like dialect.

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.

[edit] 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 to an object of type THelloWorld }
  HelloWorld.Put;                        
  HelloWorld.Free;                       { this line deallocates the THelloWorld object pointed to by HelloWorld }
end.

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

[edit] 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.

[edit] 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 support operator overloading (with different grammar, though). Delphi has also introduced many other features since version 7^[2] including generics.

[edit] See also

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

[edit] References

[edit] External links

• Introduction to Object Pascal, MacTech Vol 2 Issue 12 1985.
• Current version's Object Pascal Ref guide (PDF)
• Current version's Object Pascal Ref guide (html)

v • d • e Pascal programming language family Dialects Pascal · Object Pascal · Oxygene · Clascal · Concurrent Pascal · SuperPascal Implementations Commercial Delphi · Delphi Prism (Oxygene) · PocketStudio · HP Pascal · IP Pascal · Prospero Pascal · FrameworkPascal · C/AL Non-commercial Free Pascal (Lazarus) · GNU Pascal · Turbo51 · Virtual Pascal · MIDletPascal · Pic Micro Pascal · ACK Discontinued Apple Pascal · THINK Pascal · Turbo Pascal · Microsoft Pascal · UCSD Pascal · JRT · Pascal/mt Comparison of Pascal and C · Comparison of Pascal and Delphi