How to solve the N = 8 corner-turning problem using a butterfly network, with eight devices simultaneously transmitting data from the left-hand side and eight other devices receiving data from the right-hand side. After the three control bits, shown at the top, have looped through all eight combinations 000, 001, 010, 011, 100, 101, 110 and 111, all input devices have transmitted the required data to all output devices. The boxes (controlled swappers) have two input wires and either pass them straight through to their output wires or swap them, depending on whether the control bit (drawn as entering from above) is 0 or 1, respectively. The eight inputs are numbered in binary on the left-hand side, and we see that the first row of swappers can flip their first address bit, the second row of swappers can flip their second bit and the third row of swappers can flip their third bit.