All column outputs are low, because my code has told them to be. If I press a button, all columns are still low and one row is forced low by the button press. I then set the first column output high. So there will at this point be one column high and and the rest of the columns are still low.

Ok, that will work except in the case of multiple keys pressed.

The method of one column low at a time will handle multiple keys.

Just a very untraditional way of doing it, but there is, as we all know, more than one way to skin a cat.

Erik