Input Pin & Output Pin in Logisim

The Pin component is the primary way to feed signals into a Logisim circuit and inspect the results. When Output is false (the default Input Pin, drawn as a square box), it acts as an interactive signal driver whose bits you can toggle between 0 and 1 at any time during simulation.

To change an Input Pin value while simulating, switch to the Poke tool (the hand icon in the toolbar) and click directly on the bit inside the pin box. If you click the pin with the Select tool (arrow icon) instead, you select and move the component on the canvas or edit its attributes in the inspector rather than toggling its logic state.

Setting the Data Bits (width) attribute from 1 up to 32 turns a single-bit Pin into a multi-bit bus pin. When Output is set to true, the Pin switches from driving the wire to reading and displaying the incoming wire or bus value, which is also how Logisim grades subcircuit ports and daily challenge outputs.

Compared with other Wiring and I/O parts: an Input Pin holds whatever state you poke into it until you click it again, whereas a Button only outputs 1 while you hold the mouse button down, a Constant outputs a hardwired value that cannot be poked, and a Probe is a pure read-only display.

Tip: If clicking an Input Pin moves it instead of toggling 0 and 1, switch from the Select tool to the Poke tool in the top toolbar.