Exploring 1984 OS-9 on a 64K TRS-80 Color Computer – part 3

See also: part 1, part 2 and part 3.

Welcome back to the days when an IBM Compatible PC required a floppy disk just to start up. You would boot to PC-DOS (on an actual I.B.M. machine) or MS-DOS (for a clone, like the Tandy 1000 that had just come out in 1984 as the first PC compatible for under $1000). And … then what?

Just like there wasn’t much you could do with a PC with only a DOS boot disk, having just OS-9 is rather limited as well. Beyond typing some commands, what could you do?

There was a simple line-based text editor that would let you make text files. You could then “list” the text file and have that redirected to a printer, if you had one.

I guess you could say this was very limited word processing. Just without much word processing (though the EDIT command has search and replace functions).

There was also a 6809 assembler and debugger. You could write programs in 6809 assembly language.

And that was the very first time I ever wrote an OS-9 Level 1 assembly language program, and also the first time I ever used the asm assembler. I was more familiar with the rma assembler that came out for OS-9 Level 2 on the CoCo 3.

What else? Well, just like DOS, if you wanted to do more, you’d need software. Initially, Radio Shack didn’t sell anything for OS-9 other than BASIC09. Investing in that would allow someone who knew normal BASIC to start writing programs for OS-9. (I plan to do a “Converting Color BASIC to BASIC09” series at some point.)

But it was still neat.


Multi-user support is great, but if you only have one keyboard it won’t get you very far. But, OS-9 came with drivers for the CoCo’s banger RS-232 port, and also a “time sharing monitor” program that could monitor such serial port and then launch the “login” program if a terminal was hooked up to such serial port.

You could plug up an RS232 terminal to the CoCo’s serial port, and then launch “tsmon /t1 &” (the ampersand made the program run in the background so the shell prompt would return immediately). Now both you at the keyboard and another user via the serial port could be using the system at the same time. (Albeit at 300 baud.)


If that terminal was another CoCo, then a remote login might look like this:

Above, I added a new entry to the PASSWD file for “ALLEN” with a password, and made new directories /D0/USERS/ALLEN. I set that login entry to point to that directory so when I logged in, I would have been changed in to /d0/USERS/ALLEN ready to make new files there.

It’s a bit more work than this to be useful, but that’s basically the idea. It was really a game changer compared to using BASIC in ROM.


So what could you do with this 1984 OS-9 Level 1? Write programs in assembly, or buy BASIC09 and write programs in that langauge.

However, since text-based OS-9 applications were compatible across hardware, there were actually existing OS-9/6809 programs that could run on the CoCo. Third party software specifically for CoCo OS-9 would soon follow, which was interesting because CoCo OS-9 could do graphics.

But that’s an article for another day.

Until next time…

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