Never used this b*ttons on the calculator

M+ is Memory add, M- is Memory subtract, MR is Memory Recall, MC is Memory Clear. You can use it to calculate multiple step equations without having to write down the answer to each step e.g. ((12x12) + (6 / 2)), so you do 12 x 12 then hit M+, then do 6 divided by 2 then hit M+ again then to get the final answer come up on the screen you press MR. Then you'd have to press MC to clear the memory for the next question. I never used this being I could never be sure the Memory function still stored all the bits accurately as I went along.

Wow that could have helped me alot

I used MC all the time

Same they are for the memory