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Comment by java-man | Hacker News Reader

I don't understand why 0 and O look nearly identical.

It seems they are using the regular zero or a slashed variant depending on the risk of confusion: https://lii.enac.fr/wp-content/uploads/2021/08/B612-PolarSys...

Now that is an interesting picture! I am far from being a UI expert, but I do dabble and i would not have thought both forms of zero could be used in the same HMI display to lower cognitive load.

Very interesting! Thanks.

Different contractors, probably.

Wow that looks WAY better in the picture than in the various screenshots (and google fonts) we're all looking at. It looks very clean and legible.

Perhaps that sort of error is not a problem in this particular context. Adding slashes or dots makes the zero or oh look like an eight. This issue affected the design of the FE-Schrift font:

https://en.wikipedia.org/wiki/FE-Schrift#Development

Worth underlining that designers work very hard to understand the needs of the particular situation.

Usually type designers consider the legibility of 3, 6, 8, 9, 0 (particularly 8 and 0) to be more important than between O and 0. But for coders, the ambiguity between O and 0 is a big problem, so a designer would consider that.

An example for pilots: you are heading 180 and radio it as "one zero eight". Even if you immediately correct yourself, it's a problem.

Aviation use. They won't allow O and 0 to be valid for the same data.

So there is no need to disambiguate them.

It's funny, though, there's literally an example of this in the picture located on the ENAC project page for this font in the flight plan screen:

https://lii.enac.fr/projects/definition-and-validation-of-an...

Also seems to be more discussion of this point the last time this was posted:

https://news.ycombinator.com/item?id=37519166

It also seems like there's a "slashed zero" glyph in the font, though I don't know how to actually type it:

https://github.com/polarsys/b612/blob/master/sources/ufo/B61...

The first pic shows the slashed 0, which is what I'd expect if there's any chance of confusion.

But in general, aviation is pretty paranoid over this stuff.

I don't know how this font is encoded, but it's often the case in modern fonts that variant glyphs are mapped to the same code point (i.e. U+0030 in this case) so you can't directly type the variants. If you want to use them then your software needs to understand how to select font features.

In CSS you can use font-feature-settings.

https://developer.mozilla.org/en-US/docs/Web/CSS/@font-face/...

It's confusing and certainly non-standard, but rather than using a variant for this, the slashed zero is U+E007, in a private use area.

There seems to be an unofficial variant here that might be more useful for coding: https://github.com/carlosedp/b612

That's true of lots of fonts. I don't think contexts where you would have to distinguish between those two characters are nearly as common in aviation as they are in programming.

What would be displayed in an aircraft cockpit where this ambiguity would matter?

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