Delphi programming language 

Object Pascal refers to a branch of object-oriented derivatives of Pascal, mostly known as the primary programming language of CodeGear Delphi.

Object Pascal
Paradigm imperative, structured, object-oriented
Designed by originally by Apple and Niklaus Wirth
Typing discipline static and dynamic (dynamic typing through Variants, array of const and RTTI), strong, safe
Major implementations Delphi (x86 and .NET), Oxygene (.NET), Free Pascal (x86, AMD64/x86_64, PowerPC, ppc64, Sparc and ARM), Virtual Pascal (x86), TMT Pascal (x86), Turbo51 (Intel 8051)
Dialects Apple, Turbo Pascal, objfpc, Delphi, Delphi.NET, Oxygene
Influenced by Pascal, Smalltalk
Influenced Java, C#

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.

Contents

Early history at Apple

 This article or section contains weasel words, vague phrasing that often accompanies biased or unverifiable information. Such statements should be clarified or removed.

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.

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 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 71.

Object Pascal in the software market

Although C# and Java dominate the software industry market, Delphi has a considerable market share and strong presence2.

See also

References

  1. ^ "New Delphi language features since Delphi 7". CodeGear. Retrieved on 2008-07-06.
  2. ^ "TIOBE index". TIOBE Software. Retrieved on 2008-04-25.

External links

CodeGear

RemObjects Software

Introduction to Object Pascal

Delphi communities

Delphi's Object Pascal Language guide

Free Pascal Object Pascal reference guide

Tools For Object Pascal

GNU Pascal

paxCompiler