Accessing bit-field in C by its address

问题

What is the reason behind not allowing to access a bit field in C using its address, is it cause it might not be an address that is not system word aligned ..? or as it doesn't make sense to get bit's address within a byte...?(cause this types pointer arithmetic will be awkward ?)

回答1:

Bits do not have addresses. That's why you can't refer to them by address. The granularity of addressing is the char.

I guess the reasoning is that the language was design to match the architecture it targeted, and I know of no machine which allows addressing of individual bits.

回答2:

The smallest unit of addressable memory in C is a char, because this corresponds to the smallest unit of addressable memory on most CPU architectures.^* It doesn't make sense to talk about the address of a bit.

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_{* One could imagine a hypothetical machine that allowed addressing of individual bits, but it would be pretty esoteric.}

回答3:

In c smallest addressable unit of memory is considered a Byte. A pointer points to a memory location which can be of any data_type (a pointer is also another variable). Bits receding in byte don't have any address , rather they do have a bit position.

So basically you can not point to particular bit , you can point to a byte or whole word.

来源：https://stackoverflow.com/questions/8258483/accessing-bit-field-in-c-by-its-address