I'll throw in a plug for Wordgrinder. Nice command-line word processor that allow some simple formatting, and can export to Markdown (which you can then render more fancy-like with pandoc).
I'd recommend a Raspberry Pi instead of an Arduino / microcontroller of any sort. There are console/textmode word processors like WordGrinder that is perfect and completely distraction free. With a microcontroller you might end up having to program it from scratch, which is fine if that's your thing.
I'm in the process of building a similar thing, using a RasPi Zero W and a Waveshare 7.9" eink screen with a refreshrate of between 10-15fps, I've only got the concept going and it works nicely for writing, still thinking of how best to put together a box for it and making it mobile. Thinking of gutting an old laptop.
For a word processor, maybe have a look at wordgrinder.
For accounting, rather than a spreadsheet, maybe have a look at ledger or beancount.
It'd be easier to use an RS232 USB converter, and then use software on the PC that lets you use an RS232 device as a keyboard.
One potential option is something like a Raspberry Pi Zero. A RS232 to TTL serial converter would let you use the M100 as a serial console for the Pi, which would allow you to run word processing software like, to pick an example completely at random, WordGrinder (http://cowlark.com/wordgrinder; disclaimer: I wrote this). The Pi Zero is tiny, it's got onboard wifi, and it draws 80mA with the wifi turned off. It needs 0V and 5V, and chances are you could power it from the M100 itself. I don't know what the M100's battery compartment is like but it's not beyond the bounds of possibility that you could fit in some modern lithium polymer rechargeable batteries and a Pi Zero in there.
Plus, because there's no graphics, there's no temptation to fire up a web browser when you're supposed to be writing!
Edit: Apparently the M100 used four AAs. Nope, not getting a Pi Zero in there. They're not that small.
You may want to check out WordGrinder. http://cowlark.com/wordgrinder/
quoting its web site:
WordGrinder is a Unicode-aware character cell word processor that runs in a terminal (or a Windows console). It is designed to get the hell out of your way and let you get some work done.
WordGrinder is a word processor for processing words. It is not WYSIWYG. It is not point and click. It is not a desktop publisher. It is not a text editor. It does not do fonts and it barely does styles. What it does do is words. It's designed for writing text. It gets out of your way and lets you type.
The author wrote it to have something to write novels on.
I wrote my own word processor, thank you very much... http://cowlark.com/wordgrinder/
The actual answer is: because I am writing a compiler which I want to be able to have compile itself, and using massive tools like Java for core pieces of infrastructure renders that completely impossible. I want tools which are small and easy to adapt.
<blatant plug> I wrote my own retro word processor because I missed character cell work processors. Admittedly, for me it was InterWord on the BBC Micro rather than WordStar, but still: http://cowlark.com/wordgrinder/ </blatant plug>
There is a Windows binary, but I don't know if it runs on Win95 --- if anyone wants to try it, please get in touch...
It's a word processor called Focus Writer, with a weird theme I made pretty specifically for shooting this video. I mostly write prose, not code, so I prefer word processors to text editors. There is a command line word processor I like a lot, though: wordgrinder. While I mostly use Scrivener, I have fun occasionally working in that when I want a change of digital scenery.
en realidad el post no indaga demaciado en el tempa, aunque hace una lista con sus programas de batalla
el wordgrinder, es un programa en en ncurses al parecer programado medio en C y otro medio en lua, interesante como proyecto de programacion, aunque sinceramente utilizar un lenguaje de marcas ligeras "a pelo" y con un editor de texto, sale mas a cuenta, aca los links por si interesa, en freidera esta en los repos tal cual
http://cowlark.com/wordgrinder/ https://github.com/davidgiven/wordgrinder/tree/master/src/lua
el formato con el cual guarda el texto es bastante interesante, aunque el formateo tira de "comandos" mas que de etiquetado simple
I haven't used xbps to make packages. I have made some packages locally with make install but just for my own purposes.
To request a software you can make a pull request I believe, gotta be a git member. Some packages are specific to some distros and might need you to locally make them. Ie, I have a small love affair with wordgrinder but Void aint got it. No worries, there's still vim jeje but miss the wg. A lot of softwae missing from the repos are actually in the python/pip repos though. If you're familiar with python, it turns out many "regular" apps you use from your distro repo are just locally built python apps.
Otherwise, what apps are you looking for?