130 | R1 | R2 | R3 | R4 
 83 | 83 | 0  |    | 0
    |    | 1  | 1  | 
    |    |    |    | 1
    | 41 |    |    |   
    |    | 2  | 1  | 
    |    |    |    | 2
    | 20 |    |    |
    |    | 3  | 0  |
    | 10 |    |    |
    |    | 4  | 0  | 
    | 5  |    |    |
    |    | 5  | 1  | 3
    | 2  |    |    |
    |    | 6  | 0  | 
    | 1  |    |    |
    |    | 7  | 1  | 4
    | 0  |    |    |
    | 83 |    |    | 0
    | 211|    |    |
 211|    |    |    |

It adds a parity bit to the number

faster, lower level access

not OO or functional