The !A operation performs a bit-by-bit inversion of the value stored in the "A" register, and stores the result in a destination register, address pointer, or location in memory. For the latter, the address pointer must be setup before the ALU writes to memory.

408A - Store the result to the "A" register.
408B - Store the result to the "B" register.
408C - Store the result to the "C" general purpose register.
408F - Store the result to the "F" output high register.

4080 - Store the result to memory, at the current active address.
4081 - Store the result to address pointer 1.
4082 - Store the result to address pointer 2.