Some sort of “system program” that features a hex editor, disassembler, port monitor, etc. akin to KnightOS’ features.

https://www.ticalc.org/archives/files/fileinfo/196/19619.html

the pieces of KnightOS are maintained as separate projects under the KnightOS organization

Compatible with the TI-73. The most recent versions may support USB upload from PC, allowing this to effectively completely replace the original calculator OS.

https://knightos.org/

https://github.com/KnightOS/KnightOS (git most recent & USB, but compile difficult)

https://www.ticalc.org/archives/files/fileinfo/463/46387.html (precompiled, NO USB!!)

The only ASM shell for the TI-73 w/ dedicated programs, unless you want to count Swan or KnightOS. Has two versions, 0.2 and 0.3, with 0.3 apparently being just a test.

https://www.ticalc.org/archives/files/fileinfo/366/36618.html (0.2, for TI-OS 1.6)

https://www.ticalc.org/archives/files/fileinfo/388/38805.html (0.3, for all TI-OSes?)

A flash shell that can run Mallard programs. Little information about appearances.

https://www.ticalc.org/archives/files/fileinfo/455/45516.html

What even is this? The TI-81 has no way to communicate with a PC.

https://www.ticalc.org/archives/files/fileinfo/48/4859.html

Various text only shells that are required for many games on this thing. A few are dead, so look in…

https://www.ticalc.org/archives/files/fileinfo/226/22691.html (Ace)

https://www.ticalc.org/archives/files/fileinfo/14/1411.html (Ash)

https://www.ticalc.org/archives/files/fileinfo/286/28681.html (CrASH new for 82s)

https://www.ticalc.org/archives/files/fileinfo/87/8774.html (CrASH update)

https://www.ticalc.org/archives/files/fileinfo/87/8772.html (CrASH)

https://www.ticalc.org/archives/files/fileinfo/16/1628.html (JASS)

https://www.ticalc.org/archives/files/fileinfo/1/113.html (OS-82)

Whatever this is, it has no information.

https://www.ticalc.org/archives/files/fileinfo/50/5010.html

Allows organization of files, apparently.

https://www.ticalc.org/archives/files/fileinfo/182/18213.html

Imitates the interface of DOS.

https://www.ticalc.org/archives/files/fileinfo/352/35207.html

Imitates Windows, with a start menu, cursor, and programs slots.

https://www.ticalc.org/archives/files/fileinfo/92/9293.html

Like Windows TI, except no fancy GUI, it seems.

https://www.ticalc.org/archives/files/fileinfo/1/187.html

Appears to be imitating a Powershell prompt of some sort.

https://www.ticalc.org/archives/files/fileinfo/1/191.html

A more fancy imitation, because it has a mock Windows logo. The usual “Start” menu and nothing else…

https://www.ticalc.org/archives/files/fileinfo/76/7648.html

Yet again, imitating Windows with a Start menu and nothing else. This time, it has built in programs.

https://www.ticalc.org/archives/files/fileinfo/148/14868.html

Imitations with a start menu.

https://www.ticalc.org/archives/files/fileinfo/50/5012.html

Revolutionary, because it has icons on the desktop, plus little buttons where the clock would usually be.

https://www.ticalc.org/archives/files/fileinfo/110/11025.html

Requires CrASH. Enables I2C and Networking; to what extent is unknown.

https://www.ticalc.org/archives/files/fileinfo/109/10999.html