Logic and Colors in Logicly
Signal is represented in Logicly using colors. Wires connecting objects, and some objects themselves, may change color on the editing surface when pins change state or when a connection is created or removed.
Blue means that the signal is in the high state (true).
White means that the signal is in the low state (false).
Red means that the signal is in an unknown state. The signal could be high or low (maybe true, maybe false).
In the real world, if a gate's input pin is left "floating" (unconnected), it could pick up noise from the surrounding environment and change state unexpectedly. In other words, at any given moment, we can't be sure if the unconnected input pin has a high or low signal. That's one reason why Logicly may display an unknown state.
Similarly, the simulator assumes that all input pins start out in an unknown state before the signal begins propagating. If there is "feedback" (connections that loop back on themselves) in your circuit, some unknown states may not change when the initial signals have propagated. A reset switch or button is recommended in these cases.
For the mathematically inclined, here's the truth table that Logicly uses (Source: Wikipedia).
| A | B | A OR B | A AND B | NOT A |
|---|---|---|---|---|
| True | True | True | True | False |
| True | Unknown | True | Unknown | False |
| True | False | True | False | False |
| Unknown | True | True | Unknown | Unknown |
| Unknown | Unknown | Unknown | Unknown | Unknown |
| Unknown | False | Unknown | False | Unknown |
| False | True | True | False | True |
| False | Unknown | Unknown | False | True |
| False | False | False | False | True |