The operation is as slow as simple: assign to the variables the 0s and 1s from one row of the truth table, and follow the effect of those bits through the gates until the exit is reached.

For example, the following Figure shows how to obtain the exit of the circuit for the input 000

S_i(000) = 0 y C_i(000) = 0

Once seen how to obtain a row from the truth table, the following ones are as simple as slow to obtain.