OS9 is an operating system based around Unix specifically targetted for MC6809 based processors, hence it is written in assembler rather than C. Many of the Unix components are there including multi-tasking ability. It was developed during the late 70s/early 80s by Microware Corp who still develop it today, although now it is targetted for a range of processors including the 68xxx series. There are two OS9 variants for the 6809, Level 1 which is available for the Dragon supports up to 64K of RAM and Level 2 which is available on the CoCo 3 supports up to 16MB of RAM by using special paging hardware to switch in 64K blocks of memory at a time. OS9 Level 3 also exists but not for the 6809. Today NitrOS-9 is the modern equivalent of OS9 and is still supported and maintaned for the Dragon & CoCo platforms.
To run OS9 on a Dragon, you need a machine with 64K RAM ie. a D64 or an upgraded D32. Traditionally you also needed a disk system although today you can use Drivewire to host virtual disk images & accomplish the same thing. OS9 puts the machine into 64K RAM mode, switching out the BASIC & DOS ROMS giving you a completely new operating environment. I have written a fair amount of OS9 Level 1 software over the years, mostly in support of the additional hardware I've added to my Dragon. These include a multitude of device drivers and even a couple of file managers. You can find details & source code on these in the relevant area of the Dragon Projects pages.
On this page you can find general articles on writing OS9 software along with a couple of utilities I've written or been involved with.
OS9 Level 1 - Year 2K - some almost certainly outdated info on the original Dragon OS9 and Y2k bug
Usage: section start_line end_line < text_file eg. section 200 400 <doc1.txt - display lines 200 to 400 of doc1.txt
MS-DOS Disk Reader/Writer - read and write MS-DOS disks under OS9
Example Usage: spelldcm /h0/sty/dict ! anagram AYDUJDF > solutions- sample SCF device driver for MC6821 PIA.