Wire colors

We are now in a position to summarize the full rainbow of colors that Logisim wires can take on. The following little circuit illustrates all of them at once.

• Gray: The wire's bit width is unknown. This occurs because the wire is not attached to any components' inputs and outputs. (All inputs and outputs have a defined bit width.)

• Blue: The wire carries a one-bit value, but nothing is driving a specific value onto the wire. We call this a floating bit; some people call it a high-impedance value. In this example, the component placing a value onto the wire is a three-state pin, so it can emit this floating value.

• Dark green: The wire is carrying a one-bit 0 value.

• Bright green: The wire is carrying a one-bit 1 value.

• Black: The wire is carrying a multi-bit value. Some or all of the bits may not be specified.

• Red: The wire is carrying an error value. This often arises because a gate cannot determine the proper output, perhaps because it has no inputs. It could also arise because two components are trying to send different values onto the wire; this is what happens in the above example, where one input pin places 0 onto the wire while another places 1 onto the same wire, causing a conflict. Multi-bit wires will turn red when any of the bits carried are error values.

• Orange: The components attached to the wire do not agree in bit width. An orange wire is effectively "broken": It does not carry values between components. Here, we've attached a two-bit component to a one-bit component, so they are incompatible.

• Green-Fuchsia: This color scheme indicates that the wire was selected with the tool push (). This allows us to know the way and also the indication of the state of the line will be displayed in a small bubble and it also allows to follow a connection in a complex scheme.

Next: Self numbered label.