A lot of people never saw anything different come out of these printers.

These are built-in fonts available so the simplest devices/OS like DOS can directly print per-character (ASCII) rather than per-pixel or per-dot. You send it the signal to print an upper case letter for instance, it responds and prints the upper case letter about like a daisy-wheel printer would have done. No dots involved in the communication between the PC and the printer, other than the trigger that makes it print the right letter on the paper.

Printing per-dot was graphics mode, the PC has to send every single dot to the printer but that's what you need for real pictures.

After a while fonts appeared which you loaded in the PC, which would then send every one of their dots to the printer in graphics mode, so there was a lot fancier text output available. But it was fiddly and didn't always work right, and by that time there were newer printers having lots of those typewriter-style fonts built in. Those who couldn't get the fonts installed into their PC correctly, for the old MX and FX printers to print all fancy like the few real geeks were doing, just got a new printer instead and their office correspondence went from these bare-bones Epson fonts to pseudo-letter-quality just plugging in the new printer.

Windows 3.1 made it a little easier to get the auxiliary DOS fonts going, but people mostly had gotten newer printers by then.

By the time Windows 95 came out very few of these old printers were still being used, but there were plenty of True-Type fonts built into Windows by then, plus the built-in drivers for such old printers were very mature.

So it was never really very common knowledge, but you could just plug MX-80 series in to Windows 9x and pick any of the same fonts as you would for a laser printer, and it went bi-directional laying down overlapping dots like Adobe bricks, near-letter-quality enough to where they could hardly tell the difference once you faxed the page to somebody.

Something isn't right with this, though. I don't remember if there was a "wide" mode, but this font, while it feels very accurate, is somehow stretched wider than what would have been default. Here's an image of something from an MX-80 that looks more like what I remember: https://technicallywewrite.com/images/2024/07/epson2.png (taken from https://technicallywewrite.com/2024/07/01/dotmatrix). Still, thanks for sharing this!

EDIT: Now I know what the issue is! Per the link above: "Like other impact printers, the Epson series of dot matrix printers used a 6x9 grid to arrange the dots for each letter. Dots could also be printed halfway between each vertical line on the grid, effectively providing a higher resolution of 12x9 for each printed character." Here's an illustration: https://technicallywewrite.com/images/2024/07/epson1.png

In the late 1970s, my dad purchased an S-100 bus computer from Thinker Toys for about $3,000 (would be close to $15,000 today after adjusting for inflation). It had a Z80 microprocessor and ran CP/M. As was true of many hobbyist computers from this era, it came with full source code (in beautifully documented assembly) both for CP/M and for the BIOS. This was important because if you wanted to add peripherals or make other modifications to your computer, you had to edit the source code and recompile the BIOS.

A few years later my dad decided to buy an Epson MX-80 for his computer. The daisy-wheel and the plotter at work (he worked at SRI) just didn't cut it, I guess? This required buying a serial card for the S-100. In order to get that printer to work, he had to first, wire up a cable because the data lines from the card were on different pins in the printer. I believe there was a version of the FX-80 that came with a serial port instead of a parallel port which made some things easier. I was recruited as his assistant. Then he had to modify and recompile the BIOS. Then he had to also make some changes to CP/M. This was a process of trial and error that lasted for weeks. I remember I was away at summer camp and he sent me a letter he printed out on that printer. He was so happy that he finally got it to work.

Anyways, this resurfaced that memory and I thought I might as well share it. I still have the printout he sent me somewhere.