Hejlsberg, was written in assembly language independent of UCSD and the Zürich compilers. However, it adopted much of the same subset and extensions as the UCSD compiler. This is probably because the UCSD system was the most common Pascal system suitable for developing applications on the resource-limited microprocessor systems available at that time. The shrink-wrapped Turbo Pascal version 3 and later incarnations, including Borland's Object Pascal and Delphi and non-Borland near-compatibles became popular with programmers including shareware authors, and so the SWAG library of Pascal code features a large amount of code written with such versions as Delphi in mind. Software products (compilers, and IDE/Rapid Application Development (RAD)) in this category: Turbo Pascal – "TURBO.EXE" up to version 7, and Turbo Pascal for Windows ("TPW") and Turbo Pascal for Macintosh. Pure Pascal and HiSPeed Pascal 2 Pascal language Environment for the Atari ST range of computers. Borland Pascal 7 – A professional version of Turbo Pascal line which targeted both DOS and Windows. Object Pascal – an extension of the Pascal language that was developed at Apple Computer by a team led by Larry Tesler in consultation with Niklaus Wirth, the inventor of Pascal; its features were added to Borland's Turbo Pascal for Macintosh and in 1989 for Turbo Pascal 5.5 for DOS. Delphi – Object Pascal is essentially its underlying language. Free Pascal compiler (FPC) – Free Pascal adopted the de facto standard dialect of Pascal programmers, Borland Pascal and, later, Delphi. Freepascal also supports both ISO standards. PascalABC.NET – a new generation Pascal programming language including compiler and IDE. Borland Kylix is a compiler and IDE formerly sold by Borland, but later discontinued. It is a Linux version of the Borland Delphi software development environment and C++Builder. Lazarus – similar to Kylix in function, is a free cross-platform visual IDE for RAD using the Free Pascal compiler, which supports dialects of Object Pascal to varying degrees. Virtual Pascal – VP2/1 is a fully Borland Pascal– and Borland Delphi–compatible 32-bit Pascal compiler for OS/2 and Windows 32 (with a Linux version "on the way"). Sybil is an open source Delphi-like IDE and compiler; implementations include: WDSibyl for Microsoft Windows and OS/2, a commercial Borland Pascal compatible environment released by a company named Speedsoft that was later developed into a Delphi-like rapid application development (RAD) environment named Sybil and then open sourced under the GPL when that company closed down;