Quote from: BlackHatCoiner on June 10, 2023, 12:59:45 PM

Not sure I understand. You're saying that if I wanted a 32-bit data type, and my only data type available was unsigned char, I could design 32-bit data type by defining a struct as following?

Yup, but that would only get you like 1% of the way there (defining the struct, that is; the bulk of the work is in defining the operations).

Quote from: BlackHatCoiner on June 10, 2023, 12:59:45 PM

And so, if I wanted to store integer 2^32-1, I'd fill in each of these fields with 255?

Exactly, (255*256**3) + (255*256**2) + (255*256**1) + (255*256**0) == (1*2**31) + (1*2**30) + ... + (1*2**0) == 2**32-1 (brackets for readability).

Quote from: BlackHatCoiner on June 10, 2023, 12:59:45 PM

Theoretically, I can extend this to unlimited bits long data type (...)

Yep, but if you're looking for arbitrary precision, then it's worth studying something like GMP.

Quote from: BlackHatCoiner on June 10, 2023, 12:59:45 PM

(...) but various functions from the standard library won't work, and I'll have to rewrite them myself (...)

That's right.

Quote from: BlackHatCoiner on June 10, 2023, 12:59:45 PM

(...) whereas in C# if I'm not mistaken, such capabilities exist already.

Yup, I'm not a big C# guy, but it has BigInteger (in the System.Numerics namespace, since .NET Framework 4.0, I think).

Quote from: BlackHatCoiner on June 10, 2023, 12:59:45 PM

I'm just curious why I can't define a 256-bit or x-bit data type in C.

That's coming in C23. I'm not sure what value BITINT_MAXWIDTH will take on most compilers, but assuming it's large enough, then you'll be able to write _BitInt(256), or unsigned _BitInt(256), etc.

I can't really say that I'm a fan of this approach (especially in a systems programming language like C). Every time something is made easier for people, there's a corresponding drop in the skill level of the average practitioner. I'm not a sadist, but I do think there's harm in a situation where programmers can make heavier and heavier lifts, but have less and less idea of how things actually work.