The photo shows a 74181 wired up to a breadboard with some LEDs and DIP switches. Observe that the DIP switches positions have put
the 74181 into arithmetic mode (M = L, S0 = H, S1 = L, S2 = L, S3 = H). Since the 74181 expects
the 4-bit input words to be inverted, setting Cn = H compensates for this. The binary digit of 2 is being applied to addend
input lines A0-A3, and the binary digit of 10 is being applied to the augend input lines B0-B3, which results in an
output result of 12 (F0 = L, F1 = L, F2 = H, F3 = H). Showing that two plus ten does in fact equal twelve.