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Free Pascal (or FPK Pascal or FPC) is a free, portable, open source, Pascal and Object Pascal compiler. The 32/64-bit architecture and multi-operating system compiler implements the Pascal dialects (Turbo Pascal and Delphi) as well as some MacPascal constructs, and is available for most common operating systems.

Free Pascal used to be known as FPK Pascal, since FPK are the initials of the author, Florian Paul Klämpfl. FPK Pascal never meant "Free Pascal Kompiler". Writing "Compiler" with K is uncommon in German. To avoid this confusion, at the end of 1997 the name of the project was changed into Free Pascal Compiler (FPC).

Free Pascal comes with a text mode IDE resembling Turbo Pascal's IDE. This IDE deteriorated for some time because of a missing maintainer, but in a common effort in the second half of 2005 and the first months of 2006, most major bugs were fixed and the IDE became release-worthy again.

Like Turbo Pascal and Delphi, Free Pascal has excellent support for integration of assembly language in the Pascal code. FPC supports multiple architectures and notations in the internal assembler.

The visual parts of the Delphi libraries (the VCL) and the creation of a visual IDE and RAD are part of a separate project, Lazarus.

Language dialectEdit

FPC adopted the de facto standard dialects of Pascal programmers: the Borland dialects. (Specifically: Borland Pascal 7 and Delphi 2 for version 1.0.x, and for version 2.0.x the target versions for the Delphi compatibility changed to 6/7). However, the project has a compilation mode concept, and the developers made it clear that they would incorporate working patches for the ANSI/ISO standardised dialects to create a standards compliant mode.

A small effort has been made to support some of the Apple Pascal syntax, to ease interfacing to Mac OS (X). Since the Apple dialect implements some of the Standard Pascal features that TP/Delphi miss, FPC is a bit more ISO compatible than these.

The 2.2.x series doesn't significantly change the dialect objectives beyond D7, instead aiming for close compatibility. The project still has missing Delphi functionality, mainly compiler supported exporting of classes from shared libraries (useful for e.g. Lazarus, which implements packages of components).


The early yearsEdit

Free Pascal emerged when Borland made clear there would be no Borland Pascal 8, and the next version would be a Windows-only product (which became Delphi later on), and a student (Florian Paul Klämpfl) started working on his own compiler. The compiler was written in the (Borland) Turbo Pascal dialect from the start and produced 32-Bit code for the go32v1 DOS extender used and developed by the DJGPP project at this time. Originally the compiler itself was a 16-bit DOS executable compiled by Turbo Pascal. After two years, the compiler was able to compile itself so it became 32-bit too.


The initial 32-bit compiler was published on the net, and the first contributors joined the project. In the years after publishing on the Internet, a Linux port was made by Michael van Canneyt (a full five years before Kylix), the DOS port was adapted for use in OS/2 through the EMX extender. The DOS version also improved gradually, and migrated to the go32v2 extender. This culminated in the 0.99.5 release that was much more widely used than the versions before, and the last release aiming only for Turbo Pascal compliance: later releases would add a Delphi compatibility mode. 0.99.5 was also ported to systems using a 680x0 CPU.

With 0.99.8, the Win32 target was added, and a start was made with incorporating some Delphi features. Stabilising for a 1.0 release started, and this milestone was reached in July 2000. The 1.0.x series (and the bug-fix/stabilisation releases that followed, last, 1.0.10 in July 2003) was widely used, both as an enterprise and educational tool. For the 1.0.x releases, the port to 680x0 CPUs was redone, and the compiler produces stable code for a number of 68k Unixes and AmigaOS.

The second generation Edit

During the stabilisation of what would become 1.0.x, and specially when porting to the m68k systems, it was clear the design of the code generator was far too limited in many ways. The principal problems were that adding processors basically meant rewriting the code generator, and that the register allocation was based on the principle of always keeping three free registers between building blocks, which was inflexible and hard to maintain.

For these reasons, FPC 1.1.x branched from the 1.0.x main branch in December 1999. At first, changes were mostly cleanups and rewrite/design to all parts of the compiler, and then the code generator and register allocator were rewritten. As a bonus, remaining missing Delphi compatibility was added.

The work on 1.1.x continued slowly but steadily, and in late 2003 the PowerPC port started working, followed by ARM and SPARC ports in summer/fall 2004. The AMD64 port followed in early 2004. The AMD64 port effectively made the compiler 32/64-bit.

In November 2003, a first beta release of the 1.1.x branch was packaged, and for the occasion, the version number was changed to 1.9.0. These were quickly followed by version 1.9.2 and 1.9.4. Version 1.9.4 was special because it was the first version with Mac OS X support.

The work continued with version 1.9.6 (Jan 2005), 1.9.8 (late Feb 2005), 2.0.0 (May 2005), 2.0.2 (Dec 2005), 2.0.4 (Aug 2006), and the current stable release.

Consolidation: The 2.2 series Edit

During 2006, some of the major reworks planned for 2.2 like the rewrite of the unit system hadn't started yet, and it was decided to start stabilizing the already implemented features. This to allow a 2.2 release, and push the unimplemented features to a future 2.3/2.4 branch. Some of the motivations for this roadmap change were the needs of the Lazarus projects, particularly the internal linker, win64, wince and OS X/x86 support and features related to them (like Dwarf). After a short series of betas (2.1.2 and 2.1.4), 2.2.0 was released in September 2007. A 2.2.2 release is scheduled for first half of 2008.

The 2.2.x series vastly improve the ActiveX/COM, interface and OLE support, though bugs are still being found. The delegation to interface using the "implements" keyword is partially implemented but not complete. Aside from the language support, also the library support for ActiveX was vastly improved (and this will continue with 2.2.2). The other major highlight was the internal linker for win32/win64/CE which strongly improves linking time and memory use, and makes the compiler/link/run cycle in Lazarus more bearable. Smartlinking (dead code elimination) efficiency has also been improved.

Minor new features are improved Dwarf debug format support, and optimizations like tail recursion, omission of unneeded stackframes and temp (register) based CSE optimization. A first implementation of generics support is also available, but only for exploration purposes.

Currently it is unsure if the improved in-binary resource support in 2.3.x will be merged to 2.2.2.

The futureEdit

The following features are missing from 2.2.0 and are needed. Those marked with † are currently actively being worked on in the 2.3.1 branch.

  • Linking/debug/file formats related:
    • Improved "packages" and dynamic libraries (PIC!) support in general. Currently the Free Pascal core has no short term plans in this direction, due to practical problems for non Windows platforms.
    • Some form of Kylix compatible resources. This feature has been backported from the 2.3 branch to the 2.2 branch, and will be in 2.2.2
  • Apple Pascal related
    • Being able to pass a subprocedure to a different procedure as a procvar.
    • Objective Pascal to ease COCOA interfacing.

Some of these features, especially in the linking section, may require changes:

  • Rewrite of module (unit) handling, postponed to post 2.4


The FPC compiler's availability depends on the major version.

Version 2.3.x (development version) Edit

In addition to all targets supported by 2.2, this version supports:

  • Symbian OS - with UIQ toolkit
  • Mac OS X 64-bit (Darwin/x86_64)

Version 2.2.x (current stable) Edit

The current stable version 2.2.0 adds support for the following systems, on top of existing platforms in 2.0.x:

  • Win64
  • Mac OS X (on Intel, i386)
  • PowerPC 64-bit
  • Windows CE (Windows Mobile)
  • Nintendo Game Boy Advance (standard ARM only)
  • Nintendo DS

Version 2.0.x Edit


  • iA-32: Intel 80386, compatible processors, and later Intel processors of the same family (80486 and the Intel Pentiums).
    • AMD64: x86_64
  • PowerPC
  • ARM
  • SPARC v8 and v9

Operating systems:

  • Linux: all CPUs
  • BSD and family
    • FreeBSD
    • Darwin (PowerPC)
  • Mac OS
  • DOS; Go32V2 extender. PMode extender sometimes used for embedded systems
  • Win32 (Microsoft Windows 95 and all later versions)
  • OS/2: EMX and native
  • Novell NetWare
  • MorphOS

Version 1.0.x Edit

The previous stable release 1.0.x was available for central processors

  • Intel 80386 and compatibles
  • Motorola 680x0

and supported the following operating systems

  • Linux: x86/m68k
  • BSDs
    • FreeBSD
    • NetBSD: x86/m68k
  • DOS: Go32V2 extender. PMode extender sometimes used for embedded projects
  • Win32
  • OS/2: EMX
  • Amiga Classic, m68k

and the beta platforms:

  • BeOS, beta
  • A beta for OpenBSD/x86 existed at some point.
  • SunOS, Solaris
  • QNX
  • Windows CE

Applications software produced with Free PascalEdit

  • Pixel image editor: Photoshop-like image editor made with FPC
  • Peazip: open source archiver, made with Lazarus/FPC
  • Morfik: Morfik WebOS AppBuilder uses Free Pascal to produce the resulting CGI binaries

See alsoEdit

  • Lazarus: a Rapid Application Development (RAD) Integrated Development Environment (IDE)

External linksEdit

General IntroductionEdit

Official WebsitesEdit

Development ToolsEdit

  • FPS Complete Win32 based IDE for FPC, including debugger (trace, breakpoint and watch windows).
  • DevPascal Win32 based IDE for FPC.
  • FPCShell another Win32 FPC IDE.
  • MSEide+MSEgui - a RAD/Cross Platform GUI Development System for FPC

Sites Specialized in Game DevelopmentEdit

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