[andrewstuart2]

None of it really "matches reality." It's all binary numbers, and on a deeper level, voltages or magnetized particles.

0 is not a letter of the alphabet, but nor is 01000001 (ascii 'a').

So either the first number is special, or you look for a special number to indicate the end. Neither represents reality, because the "end" of a single group of characters is visually identical to a million white-space characters that happen to fit into the emptiness that follows.

My point being, it's probably not helpful to argue which "matches reality" when they're both just abstract representations of concepts.

[function_seven]

I was going more toward "closer to reality". But I take your point. Somewhere we're going to need extra info about the string itself, whether that extra info is a magic terminator or a magic prefix. The magic prefix gives great benefit, but also is more complex to implement if you want to store an arbitrary-length string.

[SAI_Peregrinus]

Most CPUs have a flags register, and typically have a "zero" flag which is set when the result of the last operation was zero. Zero is special in the vast majority of hardware designs. Checking for null (zero) instead of another specific value often saves a few cycles. That's where the optimization of having all FOR loops count down towards zero comes from, the check saves a cycle or two each iteration on some CPUs. The same thing happens when reading from a buffer, the load instruction will set the Zero flag when the terminating null is read.

The difference doesn't matter much on modern (non-embedded) processors, but it did make sense at the time C was designed. It matches the most common hardware design pattern better than the alternatives.