The Unified Modeling Language (UML) is commonly used in introductory Computer Science to teach basic object-oriented design. However, there appears to be a lack of suitable software to support this task. Many of the available programs that support UML focus on developing code and not on enhancing learning. Those that were designed for educational use sometimes have poor interfaces or are missing common and important features, such as multiple selection and undo/redo. There is a need for software that is tailored to an instructional environment and has all the useful and needed functionality for that specific task. This is the purpose of minimUML. minimUML provides a minimum amount of UML, just what is commonly used in beginning programming classes, while providing a simple, usable interface. In particular, minimUML was designed to support abstract design while supplying features for exploratory learning and error avoidance. In addition, it allows for the annotation of diagrams, through text or freeform drawings, so students can receive feedback on their work. minimUML was developed with the goal of supporting ease of use, supporting novice students, and a requirement of no prior-training for its use.