Comprehension of both programming and programs is a difficult task for novices to master, with many university courses that feature a programming component demonstrating significant failure and drop out rates. Many theories exist that attempt to explain why this is the case. One such theory, originally postulated by du Boulay, is that students do not understand the properties of the machine; they do not understand what they are or how they are controlling them by writing code. This idea formed the development of the notional machine, which exists solely as an abstraction of the physical machine to aid with its understanding and comprehension.ududThis work contributes a design for a new notional machine and a graphical notation for its representation. The notional machine is designed to work with object-oriented languages (in particular Java). It provides several novel contributions over pre-existing models -- while existing similar models are generally constrained to line by line operation, the notional machine presented here can scale effectively across many program sizes, from few objects and lines to many. In addition, it is able to be used in a variety of formats (in both electronic and unplugged form). It also melds together three traditionally separate diagrams that had to be understood simultaneously (the stack trace, class diagram and object heap.)ududNovis, an implemented version of the notional machine, is also presented and evaluated. It is able to create automatic and animated versions of notional machine diagrams, and has been integrated into BlueJ's main interface. Novis can present static notional machine diagrams at selected stages of program execution, or animate ongoing execution in real time.ududThe evaluation of Novis is presented in two parts. It is first tested alongside a selection of methodically chosen textbook examples to ensure it can visualise a range of useful programs, and it then undergoes usability testing with a group of first year computer science students.
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机译：对于新手来说，对程序和程序的理解都是一项艰巨的任务，许多大学课程的程序部分都显示出重大的失败和辍学率。存在许多试图解释为何如此的理论。最初由du Boulay提出的一种理论是，学生不了解机器的性能。他们不了解自己是什么，或者不知道如何通过编写代码来控制它们。这个想法形成了概念机器的发展，它仅作为物理机器的抽象而存在，以帮助其理解和理解。 ud ud这项工作为新的概念机器的设计和图形表示法做出了贡献。该概念机旨在与面向对象的语言（特别是Java）一起使用。它为现有模型提供了许多新颖的贡献-尽管通常将现有的相似模型限制为逐行操作，但此处介绍的概念机可以有效地扩展许多程序大小，从很少的对象和行到很多。此外，它可以多种格式使用（以电子形式和不插电形式使用）。它还将必须同时理解的三个传统上独立的图（堆栈跟踪，类图和对象堆）融合在一起。 ud udNovis，也是概念机的一种实现版本，也得到了介绍和评估。它能够创建概念机器图的自动版本和动画版本，并且已集成到BlueJ的主界面中。 Novis可以在程序执行的选定阶段显示静态概念机器图，或实时为正在进行的执行动画。 ud udNovis的评估分为两部分。首先对它进行测试，同时还要选择一些系统选择的教科书示例，以确保它可以可视化一系列有用的程序，然后与一组计算机科学专业的一年级学生进行可用性测试。
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