JAR Libraries

Using JAR libraries

Logisim has two types of circuit components: those that are designed as Logisim circuits, and those that are written in Java. Logisim circuits are easier to design, but they cannot support sophisticated user interaction, and they are relatively inefficient.

Logisim contains a fairly thorough collection of built-in libraries of Java components, but it can also load additional libraries written by third parties. Once you have downloaded a library, you can import it into your project by right-clicking the project in the explorer pane (the top line) and choosing Load JAR Library....

Then, Logisim will prompt you to select the JAR file, and then it will prompt you to type the class name, which will be provided by the third party. After this, the library's components will be available.

Creating JAR libraries

The remainder of this section is dedicated to a series of thoroughly commented examples illustrating how to develop Logisim libraries yourself. You should only attempt this if you're an experienced Java programmer. You will find the documentation beyond these examples fairly meager.

You can download a JAR file that allows these examples to be imported into Logisim via the Logisim Web site's Links section. That JAR file also contains the source code contained in these examples; this source code is in the public domain. (In contrast, the source code to Logisim is released under the GNU Public License.)

Byte Incrementer

Illustrates the essential components of any component type using a simple example of a component that inputs one 8-bit value and emits that value plus one.

Library Class

Illustrates how to define a library. This is the entry point for any JAR file - the class whose name the user enters when loading the JAR library.

General Incrementer

Illustrates how to make components customizable through the usage of attributes, by generalizing the byte incrementer to work with any bit width for the input and output.

Basic Counter

Illustrates how to make a component that has internal state, in particular an 8-bit counter that remembers a current value and increments each time its clock input encounters a rising edge.

Counter

Demonstrates a complete, fairly sophisticated component with which the user can interact. It implements a counter (where the number of bits remembered is customizable) where the user can edit the current value by clicking on it with the Poke Tool and typing a value.

Guidelines

General information for those developing third-party libraries.

Next: Byte Incrementer.