For each floor, there are Allowed calls masks
C = Car call
U = Up hall call
D = Down hall call
E = Emergency (hospital or VIP) call
There are front and rear Allowed call masks at each floor, so the Service Tool/OFT screen shows "CUDE CUDE", with the front call types first, and the rear call types second. When speaking people will say they are "Coo - Dee" masks because that's about the best way to pronounce the initials for "CUDE"
If you had floor 5 showing 1110 0000, that would mean that that you had a front car call, up hall call and down hall call at that floor, which is a pretty typical for an intermediate floor. At the bottom floor, you wouldn't have any "D" calls, and at the top floor you wouldn't have any "U" calls.