Hal is correct, the accumulator is just a register and as such can be used to store data.

However, its a special register because the data paths into it, can flow through the arithmetic unit allowing contents to be alterred before entering or re-entering the accumlator.

Usually you don't want to use the accumulator unless you are transporting bytes through it for special opcodes or if you are manipulatin the contents with the arithmetic unit.

While you CAN do so, you'll often find the stored data in the way.

aka j