通过其地址访问C中的位字段

Question

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 ?)

Answer 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.

Answer 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.}

Answer 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.