Open Watcom C/C++
Original author	Watcom
Developers	Sybase,SciTech Software
Initial release	1988; 37 years ago (1988)
Stable release	2.0 (continuous updates) / December 4, 2024; 11 months ago (2024-12-04)[1]
Repository	github.com/open-watcom/open-watcom-v2
Written in	C,C++
Operating system	DOS,Windows,OS/2,Linux
Platform	x86,IA-32,x86-64
Size	66–84 MB
Type	Integrated development environment
License	Sybase Open Watcom Public License version 1.0
Website	openwatcom.org open-watcom.github.io

Watcom C/C++ (currentlyOpen Watcom C/C++) is anintegrated development environment (IDE) product fromWatcom International Corporation for theC,C++, andFortranprogramming languages. Watcom C/C++ was a commercial product until it was discontinued, then released under theSybase Open Watcom Public License as Open Watcom C/C++. It features tools fordeveloping anddebugging code forDOS,OS/2,Windows, andLinuxoperating systems, which are based upon 16-bitx86, 32-bitIA-32, or 64-bitx86-64 compatible processors.

In 2000,Sybase, who owned Watcom International Corporation halted the commercial sale of the Watcom C/C++ andFortran compilers. In 2003, SciTech Software Inc, a customer of Sybase, negotiated wth Sybase, to have the code for the compilers released as an open source project under a new name, Open Watcom.^[2] The Watcom C/C++ compiler and the Watcom Fortran compiler were made available free of charge as theOpen Watcom package.

The last stable version endorsed by the original openwatcom.org team was 1.9, released in June 2010.^[3][4]

A community-basedforked version 2.0 (with continuous updates under the same version moniker) was released after the original codebase was seemingly no longer developed by the original team. It includes miscellaneous bugfixes, supports 64-bit hosts (Windows and Linux), built-in text editor, 2-phase build system, and has a DOS version that supportslong filenames (LFN).^[5]

TheOpen Watcom Wiki has a comprehensive history.^[6][4]

TheOpen Source Initiative has approved the license asopen source, butDebian,Fedora and theFree Software Foundation have rejected it because "It requires you to publish the source code publicly whenever you “Deploy” the covered software, and “Deploy” is defined to include many kinds of private use."^[10]

The compiler can be operated from, and generate executable code for, theDOS,OS/2,Windows, Linuxoperating systems. It also supportsNLM targets forNovell NetWare. There is ongoing work to extend the targeting toLinux^[11] and modernBSD (e.g.,FreeBSD) operating systems, running onx86,PowerPC, and other processors.

The code is portable and, like many other open source compiler projects such asGCC orLCC the compiler backend (code generator) is retargetable.

In the mid-1990s some of the most technically ambitiousDOScomputer games such asDoom,^[6]Descent,^[6]Duke Nukem 3D,^[6]Rise of the Triad,^[12] andTomb Raider were built using Watcom C/C++ using theDOS/4GWprotected mode extender with the Watcom compiler.

It was used to port the gameRetro City Rampage to DOS in 2015.^[13]

It was used byVirtualBox to compile theBIOS.^[14]

Current development forFreeDOS requires that all Csource code must be compilable by Open Watcom C.^[15]

Open Watcom is the recommended compiler for application and driver development for the OS/2-basedArcaOS operating system.^[16]

Open Watcom's syntax supports many conventions^[which?] introduced by other compilers, such asMicrosoft's andBorland's, including differing conventions^[which?] regarding (for instance) the number of leading underscores on the "asm" tag. Code written specifically for another compiler rather than standard-compliant C or C++ will often compile with the Watcom compiler.

The C compiler supportsANSI C (C89, C90, ISO C) standard by default.

Open Watcom supports partial compatibility with theC99 standard. It implements the most commonly used parts of the standard, including inline variable declaration. However, they are enabled only through the undocumented command-line switch "-za99" (which needs to be added to the "Other options" field in "4. Miscellaneous Switches" panel in the GUI). In a more recent version of Open Watcom 2.0, a check box was added for C99 in the "2. Diagnostics Switches" panel in the GUI. Three C99 features have been bundled asC90 Extension since pre-v1.0: C++ style comments (//), flexible array members, trailing comma allowed in enum declaration.^[17]

The compiler currently doesn't support any new^[when?] majorC11 features, though the C library does include "Safe C" functions. It is specified in ISO/IEC TR 24731-1^[18][19] and known as "Bounds-checking interfaces (Annex K)" in C11. Some function name examples are strcpy_s(), memcpy_s(), printf_s().^[20] This library was released along with Open Watcom 1.5 in April 2006.

In a February 1989 overview of optimizing C compilers,BYTE praised Watcom C 6.5's "unmatched execution speed" and noted that it was the mostANSI C-compliant. The magazine advised, "If speed is absolutely critical andOS/2 compatibility isn't, choose Watcom".^[21]

• Open Watcom Assembler

• Watcom C/C++ Gets a New Face – review in October 1994 BYTE magazine
• The WATCOM C/C++ Programmer's FAQ

Current

• Open Watcom v2 onGitHub
• Open Watcom v2

Archives

• Open Watcom 1.9 onGitHub
• Open Watcom 1.9 – (Archived March 17, 2015, at theWayback Machine)
• Sybase Watcom C/C++ version 11.0 – (Archived October 13, 1999, at theWayback Machine)

• C (programming language) compilers
• C++ compilers
• Formerly proprietary software
• 2003 software

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