The hardware uses 4-bit inputs to the memory of the registers (two). the three buttons on the left are for the register number (it’s just 0 & 1). The buttons to the right of it is the enable lever. After, the four buttons on the right of that is are the bits. Finally, the buttons on the very right is the output control. Another thing to mention is that you need to enable and select the register before you can save the bits.