OF-Link allows one (or more) instances of the TSC 6809 FLEX operating system to run under OS-9/6809 Level II (or NitrOS-9/6809 Level 2) on the Radio Shack Color Computer 3 (CoCo 3).
OF-Link is an OS-9 module that acts as an interface between the FLEX and OS-9 operating systems. It permits FLEX and FLEX programs to run on (Nitr)OS-9, in a similar fashion to the Wine compatibility layer that lets Microsoft Windows applications run on Linux. OF-Link allows you to run many of your existing FLEX programs under (Nitr)OS-9 without requiring you to buy OS-9 versions of them.
OF-Link was first advertised in RAINBOW magazine in the September 1988 issue. It was enthusiastically reviewed on pages 16-17 in the April 1989 issue of '68' Micro Journal. The review had a few minor errors, and subsequent updates eliminated some reported problems:
Only version 0.5 was developed and distributed. Sales of OF-Link were so few that I couldn't afford to spend the required time to finish implementing the planned enhancements to create version 1.0. OF-Link was an interesting and useful product, but a marketing and financial flop.
Programs that run under FLEX can be downloaded from various sites such as here and here. Archived issues of '68' Micro Journal have much useful information on FLEX and programs for FLEX, several FLEX manuals can be downloaded, and you can read about the history of FLEX. You can even find source code (well commented disassembly) for FLEX v3.01 (files FLEX.TXT and FLEXFMS.TXT in flex_srces.dsk).
Since the TSC FLEX operating system may now be freely distributed, as may the NitrOS-9 operating system, and now also the SDisk3 floppy disk driver, I am able to supply an Ease of Use (EOU) disk image (see below). This is much easier to use than the software on my original distribution disk which required many installation steps. The EOU disk is bootable and ready to run, and includes the SDisk3 driver pre-installed in the NitrOS-9 OS9Boot file, a shell procedure file that calls a pre-configured version of OF-Link, and a FLEX virtual disk containing the linked FLEX v3.01 operating system and related utilities. While I don't have a CoCo 3 to test it on, it runs just fine on the VCC 2.0.1b CoCo 3 emulator.
Peter Stark developed an operating system called STAR-DOS (later renamed to SK*DOS) that was mostly compatible with FLEX, and also works with OF-Link:     
The source code for OF-Link won't be available for a while. I haven't yet found a copy that matches the distributed binaries, and the most recent copy of the source code contains lots of modifications that are incomplete.
When you read the two manuals shown below, display them at a large size. The Letter Gothic font I used makes it very hard to distinguish between a period and a comma when displayed at a reduced size. If anyone knows of a better version of this font, please let me know. The Letter Gothic font that was printed on daisywheel printers in the 1980's was much better.
|OF-Link User's Manual.
|OF-Link Additional Notes.
|DSK image (35T/SS/DD CoCo OS-9 format) of original OF-Link
|DSK image (40T/SS/DD CoCo OS-9 format) of EOU version of
OF-Link that is ready to boot NitrOS-9 and FLEX, with instructions.
|DSK image (40T/SS/DD CoCo OS-9 format) of source code for
OF-Link and related programs.
(not available yet)
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