TopSpeed C

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A C development system for 16 bit OS/2, Windows and DOS code, in addition to supporting Psion series 3 development if bought as a part of the PSION SDK. The TopSpeed C compiler can be run as a native OS/2 application or by cross compiling from DOS. Notable for being the first PC C compiler that was fully ANSI C compliant, and the first one on any system to get ISO C90 validation. System now owned by Soft Velocity who use it as a utility development system for their Clarion database product and an OS/2 compatible product is no longer being offered. Originally a development of the TopSpeed Modula-2 toolkit and shares the same environment and back-end

The later versions of the TopSpeed C compiler are considered to be very good unlike their C++ counterpart, although by now completely outdated.

The TopSpeed development environment

One unusual aspect of the TopSpeed system was that you could buy variants of the development system for Modula-2, C++ and Pascal in addition to the C compiler and they all shared a back end. Not only could you call C, C++ or Pascal code from the Modula compiler (and vice versa) but with later incarnations of the system you could mix and match the languages in one source file without resorting to any containers. An unique feature in its time and only one or two other development systems have offered similar features since. After Clarion took over the sales of the TopSpeed system the Clarion 4GL database language was ported to the TopSpeed system (and remains based on it to this day) and became one of the interchangeable front ends.

The development environment also contained an automatic make facility, an editor, librarian, source-level debugger and sundry minor utilities, and was available in two versions the standard version contained the environment, tools and compiler while the TopSpeed Extended Edition basically bundled the standard edition with TopSpeed TechKit.

Another unusual and somewhat unique aspect of the system was its ability to make multi-threaded code and dynamic libraries (DLLs) for DOS. The TopSpeed system was developed under OS/2 v1.x and the developers were so taken with the threading model that they duplicated it for the DOS environment giving you not only the obvious benefit of being able to make multi-threaded DOS applications but also the option of making portable multi-threaded apps since the TS version for doses copied the OS/2 version down to a tee.


TopSpeed C was also the basis for the PSION SIBO C SDK for the PSION series 3 handheld computers, it was basically the TopSpeed C toolkit with a few extra libraries and header files for developing for the SIBO OS, the processor on the S3 is a 80186 superset NEC V30H, note that nothing was removed from the standard TopSpeed C package so in addition to allowing you to develop software for the PSION S3 you could develop for the PC as well. It came in two editions, the SIBO C SDK Standard Edition was a standard version of the Clarion TopSpeed C package with the S3 libs and header files, while the SIBO C SDK Professional Edition also included the TopSpeed TechKit which was the equivalent to a "TopSpeed Extended Edition" in that it contained a macro assembler and the sources to all PC and PSION libraries in addition to just the libraries.


  • 1989: 1.03
  • Latest version: 3.10.002


  • For Windows 3.x or Win-OS/2 programming the TopSpeed TechKit is required, but the tools from it integrate into the TopSpeed environment.
  • Although you can develop OS/2 Presentation Manager applications without the OS/2 SDK, it is highly recommended that you use it since the PM support of TopSpeed C is rather weak in the parts were tools from the SDK already existed.
  • DOS 3.0 or later and/or OS/2 1.3 or later.