Free Pascal

Free Pascal was created when Borland clarified that Borland Pascal development for DOS would stop with version 7, to be replaced by a Windows-only product, which later became Delphi.

Student Florian Paul Klämpfl began developing his own compiler written in the Turbo Pascal dialect and produced 32-bit code for the GO32v1 DOS extender, which was used and developed by the DJ's GNU Programming Platform (DJGPP) project at that time.

Originally, the compiler was a 16-bit DOS executable compiled by Turbo Pascal. After two years, the compiler was able to compile itself and became a 32-bit executable.

The initial 32-bit compiler was published on the Internet, and the first contributors joined the project. Later, a Linux port was created by Michael van Canneyt, five years before the Borland Kylix compiler became available.

The DOS port was adapted for use in OS/2 using the Eberhard Mattes eXtender (EMX) which made OS/2 the second supported compiling target. As well as Florian Klämpfl the original author, Daniël Mantione also contributed significantly to make this happen, providing the original port of the run-time library to OS/2 and EMX. The compiler improved gradually, and the DOS version migrated to the GO32v2 extender. This culminated in release 0.99.5, which was much more widely used than prior versions, and was the last release aiming only for Turbo Pascal compliance; later releases added a Delphi compatibility mode. This release was also ported to systems using Motorola 68000 family (m68k) processors.

With release 0.99.8 the Win32 target was added, and a start was made with incorporating some Delphi features. Stabilizing for a non-beta release began, and version 1.0 was released in July 2000. The 1.0.x series was widely used, in business and education. For the 1.0.x releases, the port to 68k CPU was redone, and the compiler produced stable code for several 68k Unix-like and AmigaOS operating systems.

During the stabilization of what would become 1.0.x, and also when porting to the Motorola 68k systems, it was clear that the design of the code generator was far too limited in many aspects. The principal problems were that adding processors 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 difficult to maintain.

For these reasons, the 1.1.x series branched off from the 1.0.x main branch in December 1999. At first, changes were mostly clean-ups and rewrite-redesigns to all parts of the compiler. The code generator and register allocator were also rewritten. Any remaining missing Delphi compatibility was added.

The work on 1.1.x continued slowly but steadily. In late 2003, a working PowerPC port became available, followed by an ARM port in summer 2004, a SPARC port in fall 2004, and an x86-64-AMD64 port in early 2004, which made the compiler available for a 64-bit platform.

In November 2003, a first beta release of the 1.1.x branch was packaged and numbered 1.9.0. These were quickly followed by versions 1.9.2 and 1.9.4; the latter introduced OS X support. The work continued with version 1.9.6 (January 2005), 1.9.8 (late February 2005), 2.0.0 (May 2005), 2.0.2 (December 2005), and 2.0.4 (August 2006).

In 2006, some of the major reworks planned for 2.2, such as the rewrite of the unit system, had still not begun, and it was decided to instead start stabilizing the already implemented features.

Some of the motives for this roadmap change were the needs of the Lazarus integrated development environment project, particularly the internal linker, support for Win64, Windows CE, and OS X on x86, and related features like DWARF. After betas 2.1.2 and 2.1.4, version 2.2.0 was released in September 2007, followed by version 2.2.2 in August 2008 and version 2.2.4 in March 2009.

The 2.2.x series vastly improved support for the ActiveX and Component Object Model (COM) interface, and Object Linking and Embedding (OLE), though bugs were still being found. The delegation to interface using the implements keyword was partly implemented, but was not complete as of March 2011.[1] Library support for ActiveX was also improved.

Another major feature was the internal linker for Win32, Win64, and Windows CE, which greatly improved linking time and memory use, and make the compile-link-run cycle in Lazarus much faster. The efficiency for smart-linking, or dead code elimination, was also improved.

Minor new features included improved DWARF (2/3) debug format support, and optimizations such as tail recursion, omission of unneeded stack frames and register-based common subexpression elimination (CSE) optimization. A first implementation of generic programming (generics) support also became available, but only experimentally.

The 2.4.x release series had a less clear set of goals than earlier releases. The unit system rewrite was postponed again, and the branch that became 2.4 was created to keep risky commits from 2.2 to stabilize it. Mostly these risky commits were more involved improvements to the new platforms, Mac PowerPC 64, Mac x86-64, iPhone, and many fixes to the ARM and x86-64 architectures in general, as well as DWARF.

Other compiler improvements included whole program optimization (WPO) and devirtualization and ARM embedded-application binary interface (EABI) support.

Later, during the 2.2 cycle, a more Delphi-like resource support (based on special sections in the binary instead of Pascal constants) was added. This feature, direly needed by Lazarus, became the main highlight of the branch.

Other more minor additions were a memory manager that improved heap manager performance in threaded environments, small improvements in Delphi compatibility such as OleVariant, and improvements in interface delegation.

On January 1, 2010, Free Pascal 2.4.0 was released, followed on November 13, 2010, by bug fix release 2.4.2, with support for for..in loops, sealed and abstract classes, and other changes.[2]

In January 2012, Free Pascal 2.6 was released. This first version from the 2.6 release series also supported Objective Pascal on OS X and iOS targets and implemented many small improvements and bug fixes. In February 2013, FPC 2.6.2 was released. It contained NetBSD and OpenBSD releases for the first time since 1.0.10, based on fresh ports. In March 2014, the last point release in the 2.6 series, 2.6.4, was launched, featuring mostly database (fcl-db) updates.

Version 3.0.0 was released on November 25, 2015 and was the first major release since January 1, 2012. It contains many new language features: FPC New Features 3.0

Version 3.0.2 was released on February 15, 2017 and includes bug fixes and minor compiler updates.
Version 3.0.4 was released on November 28, 2017.
It includes many language improvements over previous versions like an internal linker for Executable and Linkable Format (ELF), Arm AARCH64 for iOS and Linux, a revived i8086 platform, extended libraries and much more.

The next major release, version 3.2.0, was published on June 19, 2020. It introduced a plethora of new language features including generic routines, standard namespaces, managed records and expanded functionality for dynamic arrays, in addition to the advent of new standard units and the support of additional platforms[3].

• Official website FPC
• Official website Lazarus RAD IDE

• Official documentation
• Modern Object Pascal Introduction for Programmers - by Michalis Kamburelis

• Pascal Game Development
• Pascal Gamer Magazine
• FPC 4 GBA Programming Tutorial – an extensive tutorial into game programming on the Game Boy Advance with Free Pascal