The explorer pane

Libraries contain components that can be dropped into circuits. They are displayed as folders in the explorer pane; to access a library's components, you have only to double-click the corresponding folder. Below, I have opened the Gates library and selected the NAND tool from it. You can see that Logisim now stands ready to add NAND gates into the circuit.

If you look through the choices in the Gates library, you'll notice that there was no need for us to develop a XOR circuit earlier: It's built into Logisim.

When you create a project, it automatically includes the Base and Gates libraries. But Logisim includes many other libraries, too: To load one, go to the Project menu, in the Load Library submenu, and choose Built-in Library.... A dialog box will appear allowing you to choose which libraries you want to add. If you choose Plexers, for example, then you will be able to add multiplexers, demultiplexers, and decoders. You can load as many libraries as you like.

In the Load Library submenu, you can see that Logisim has three categories of libraries.

Built-in libraries are libraries that are distributed with Logisim. These are documented in the Library Reference.
Logisim libraries are projects built within Logisim and saved to the disk. You can develop a set of circuits in a single project (as described in the Subcircuits section of this guide) and then use that set of circuits as a library for another projects.
JAR libraries are libraries that are developed in Java but not distributed with Logisim. You can download JAR libraries that others have written, or you can write your own as described in the JAR Libraries section of this guide. Developing a JAR library is much more difficult than developing a Logisim library, but the components can be much fancier, including things like attributes and interaction with the user. The built-in libraries (other than Base) were written using the same API as JAR libraries can use, so they aptly demonstrate the range of functionality that the JAR libraries can support.

When loading a JAR library, Logisim will prompt you to select the JAR file, and then it will prompt you to type a class name. This class name should be provided by whoever distributed the JAR file to you.

To remove a library, choose Unload Library... from the Project menu. Logisim will prevent you from unloading libraries that contain components used in a circuit, that appear in the toolbar, or that are mapped to a mouse button.

Incidentally, a library technically contains tools, not components. Thus, in the Base library you'll find the Poke Tool (), the Select Tool (), and other tools that don't correspond directly to individual components. Most libraries, though, contain only tools for adding individual components; all built-in libraries other than the Base library are like this.

Next: The attribute table.