This group of instructions performs arithmetic operations on data in registers and memory.
Most of the instructions in this group affect the flag bits according to the standard rules.
All subtraction operations are performed via 2's complement arithmetic and set the carry flag to one to indicates a borrow and clear it to indicate no borrow.
ADD r (Add Register)
The content of register r is added to the content of the accumulator. The result is placed in the accumulator.
