Error Control

In class we made a trick with parity cards. We set black and white cards in a 7 by 7 grid and we were trying to make the black cards even so that each row had an even number of black cards going down and across. We then added another row to the grid and had to make it even, for example if there were 3 black cards we add another row to make the number even, into 4 black cards. The black and white cards represent the 1 and 0 on a computer.

Here is a screenshot of the parity trick.