dillera / nitros9

NitrOS-9 Operating System

The NitrOS-9 Repository (on GitHub)

NitrOS-9 is a community-based distribution of the Microware OS-9 operating system for the Motorola 6809 that was introduced in the late 1970s and sold into the 1980s.

The Hitachi 6309, which contains additional registers and enhanced instructions, is also supported.

Here are the current ports of NitrOS-9:

Computer	Port	Processor
TRS-80 Color Computer	NitrOS-9 Level 1	6809 & 6309
Radio Shack Color Computer 2	NitrOS-9 Level 1	6809 & 6309
Tandy Color Computer 3	NitrOS-9 Level 2	6809 & 6309
CoCo3FPGA	NitrOS-9 Level 2	6809
Dragon 64 & Tano Dragon	NitrOS-9 Level 1	6809
Dragon Alpha	NitrOS-9 Level 1	6809
Atari w/ Liber809	NitrOS-9 Level 1	6809
Corsham 6809 SS-50	NitrOS-9 Level 1	6809
Foenix F256 with FNX6809	NitrOS-9 Level 1 & 2	6809

Downloading and Building

To build NitrOS-9, you need the following:

• lwtools. This package contains the required 6809 assembler and linker.
• ToolShed. ToolShed provides file system tools for creating disk images, copying files to and from those disk images, and more.

Once downloaded and installed, you can build the entire project:

export NITROS9DIR=$HOME/nitros9
make

The result is a number of disk images (ending in .dsk) that can be used on real floppy drives, emulators, and DriveWire.

Contributing

If you wish to contribute, please fork the repository and submit pull requests.

Also, assembly source code is formatted to the following specifications:

• Spaces only (no tabs)
• Labels start at column 1
• Opcodes start at column 21
• Operands start at column 31
• Comments start at column 51

Put this file in your .git/hooks folder to ensure that any source code you submit is automatically formatted.

Coding Style Guidelines

Here are some general coding guidelines for the project.

Add a comment to every line of assembly

Having a comment on each line of assembly may seem excessive, but doing so keeps the meaning behind flow of the code intact and gives the reader a clear understanding of what is happening.

Make comments meaningful

Take time to write clearly about what a line of code is doing. Avoid repeating the obvious, if possible.

Instead of this:

     clra        clear A

do this:

     clra        set the path to standard input

Write comments in lowercase and don't use punctuation

Comments may or may not be complete sentences; as such, dispense with the formalism of capitalization and punctuation.

Instead of this:

     ldb   #E$PNNF      Prepare the "pathname not found" error.

do this:

     ldb   #E$PNNF      prepare the "pathname not found" error

Use full words

Avoid abbreviations. Spelling out words increases the readability of the comments.

Instead of this:

     pshs  d,x,y,u      push regs
     leax  ,u           load path desc ptr in X

do this:

     pshs  d,x,y,u      save the registers on the stack
     leax  ,u           load the path descriptor pointer in X

Ensure an empty line is at the end of a source file

Adding an empty line to the end of a source file ensures that some programs that parse the input do not abandon any important information on the last line.

Instead of this:

     rts

do this:

     rts