"The Treeboard was the jewel in the crown of Zeta BBS. It was a public message board, as all BBSs needed, but with a difference. It used a tree hierarchy of topics and users could create their own topics. Like the "room" idea of the Citadel BBS, which came well before Zeta, but a little more nerdy as a person who didn't like, say, sports, could skip sports at the top level and that would avoid all sporting-type discussions."
"The topics were organised as a tree. In the first incarnation I used a single 8-bit byte for each topic code, organised bitwise as AAABBBCC, where AAA represents the major category of the tree: 00100000 was a top-level category, 00100100 was a second-level category under that, and 00100101 was a third-level category. You can see that the system is limited to 7 top-level categories, 7 x 7 mid-level categories, and 7 x 7 x 3 third-level categories, for a grand total of 203 if the tree was filled evenly. In the second incarnation I realised that keeping the hierarchy information in the topic code byte itself was inefficient and so I made that a simple integer (extending the range of the system to 255 total categories) and made some other arrangement to store the category structure."
"Treeboard, or BB as it was called on the system, also had quite an advanced user input routine. One could use line commands (pressing enter after each line) or one could press the key while the menu was being output, and cancel the menu and jump straight to the requested function. One could also string commands together in line-input mode, by separating them with semicolons."
"Getting my Z80 software running on this system was quite an achievement for me; I did a direct instruction-by-instruction translation for the bulk of the code, and the operating system differences were handled by a compatibility layer." - Nick Andrew
From Jason: The code below is not the exact original code that was written for the Heathkit, but it's the same author and a port, so it's the best we'll be seeing. Every indication is that Nick used most of his original code, anyway.