The ADD instruction adds the "A" and "B" registers together, and stores the result to a register, counter, or location in memory. For the latter, the address pointer must be setup before the ADD writes to memory.

410A - Store the result to the "A" register.
410B - Store the result to the "B" register.
410C - Store the result to the "C" general purpose register.
410F - Store the result to the "F" output high register.

4100 - Store the result to memory, at the current active address.
4101 - Store the result to address pointer 1.
4102 - Store the result to address pointer 2.