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Comment by bandyaboot | Hacker News Reader

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bandyaboot·

> In the most popular character encoding, UTF-8, character number 65 ("A") is written:

> 01000001

> Only the second and final bits are 1, or "on".

Isn’t it more accurate to say that the first and penultimate bits are 1, or “on”?

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It depends on whether your bit numbering is like x86 (your description), or PowerPC (left most bit is 0).

Basically everyone uses x86 bit numbering. It has the pleasant property that the place value of every bit is always 2^n (or -2^n for a sign bit), and zero-extending a value doesn't change the numbering of its bits.

Sure, it is by far the industry standard.

It works much better for handling discrete integers.

Once you get into bitfield instructions it is nice to have bit 0 be the "left most bit".

It's a mistake to call it x86 bit numbering, it's way older than that.

The more I thought it through, even assuming x86, I guess there’s just no “correct” way to casually reference bit positions when we read them in the opposite order from the machine. Are they being referenced from the perspective of a human consumer of text, or the machine’s perspective as a consumer of bits? If I were writing that content, I’d have a difficult time deciding on which to use. If I were writing for a lay person, referencing left-to-right seems obvious, but in this case where the audience is primarily developers, it becomes much less obvious.

Thanks for giving me an example of an architecture where the bits are labelled backwards, I'd never encountered that before. I've always appreciated that the bit number represents 2 to the power of that number.

This confused me too. Until reading this I didn't even think much about how I read binary numbers right-to-left by default.

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