The 8-bit Intel 8051 family provides a dedicated bit-addressable memory space (addresses 20h-2Fh in internal RAM), giving 128 directly addressable bits. Used them for years. I'd imagine many microcontrollers have bit-width variables.

bit myFlag = 0;

Or even return from a function:

bit isValidInput(unsigned char input) { // Returns true (1) if input is valid, false (0) otherwise return (input >= '0' && input <= '9'); }

[–] [email protected] 16 points 1 day ago (2 children)

Nothing like that in ARM. Even microcontrollers have enough RAM that nobody cares, I guess.

[–] [email protected] 10 points 1 day ago

ARM has bit-banding specifically for this. I think it’s limited to M-profile CPUs (e.g. v7-M) but I’ve definitely used this before. It basically creates a 4-byte virtual address for every bit in a region. So the CPU itself can’t “address” a bit but it can access an address backed by only 1 bit of SRAM or registers (this is also useful to atomically access certain bits in registers without needing to use SW atomics).

[–] [email protected] 1 points 1 day ago

Tell this to the LPC1114 I'm working with. Did you ever run a multilingual GUI from 2kbytes RAM on a 256x32 pixel display?

[–] [email protected] 13 points 1 day ago

We could go the other way as well: TI's C2000 microcontroller architecture has no way to access a single byte, let alone a bit. A Boolean is stored in 16-bits on that one.

[–] jkercher 5 points 1 day ago

And, you can have pointers to bits!