dimming and running LEDs

Using Arduino LEDs and Multiplexing
9

CrossRoads:
Change this to

pinMode(rSwitch[a], INPUT_PULLUP); // enable internal pullups

and then read if they got pulled Low & act on that:

if(digitalRead(rSwitch[0]) == LOW) {

I dun understand this , does the INPUT_PULLUP make a difference ?
If I change the rSwitch into pullup, do I have to change the ON/OFF button as well ??