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[ Index | Introduction | Expositive | Demonstrative | Interactive | Practical | Conclusion | References ]

The Expositive Methodology

        The first methodology analyzed is called expositive. Theory, definitions, hints and many other features that translate traditional textbooks in "electronic books" are typical examples of expositive materials. In our course a hypertextual environment is the default choice, with its capability of structuring text, images and links [10], [11].
        It must be stressed that delivering expositive material with a multimedia computer instead of the classical communication media (print or speech), does not modify the position of the learners and does not remove the risk that they behave as passive observers.


        In our past experience of courseware developers we have noticed that hypertext did not prove itself very successful with students [12]. Even if the use of the hypertext as the main vehicle to convoy information to the learner showed some advantages over a textbook [13] under the point of view of material organization, indexing and search facilities, our students still preferred to learn the theory on their class notes. Consequently, in successive revisions of the courseware, the hypertext has been enhanced by reducing the number of static words on the screen, replacing them with figures, schematics and pop-up windows. In synthesis, hypertext function is to provide the framework of the lesson and to link together animation and local tools that provide a more operational explanation, acting therefore as the connective tissue between the learning tools [14].
        Fig. 2 represents an example of our implementation of the guidelines described above. A textual explanation is present on the left end side and can be scrolled independently of the picture on the right end side. Navigation buttons, on the bottom, are standard components of the GUI. The combination of text and figure explains the concept of two-dimensional memory addressing. The page shown in Fig. 3 follows immediately in the pedagogical sequence the one described in Fig. 2. The same concept of two-dimensional memory addressing is explained with the use of a learning tool that encourages the learner to verify actively the concept. The binary values of the memory address lines can be set by the student with a mouse click. The number and position of the decoders output lines change accordingly. The HELP button provides instruction on how to operate the tool.
        The screen-shots presented here as static figures are part of the courseware. The reader can take the role of the learner by running a working example [15].


        The hypertextual structure of our courseware has been enriched with the animation of most of the concepts, networks and algorithms. Animation targets specifically the understanding phase of learning, trying to form an intuitive idea of a concept. Some descriptions of processes that can be difficult to explain by text only become, in fact, very simple and intuitive if the text-based description is substituted, or integrated, with direct animation. This feature is especially useful when exposing fundamental concepts. A field where animation is particularly useful is the introduction to Finite State Machine (FSM). In our course, digital systems are represented with the model of the FSM and the Algorithmic State Machine (ASM) [16] method is applied to both Moore and Mealy machines. Therefore, an introductory course like ours takes the most advantage of animation, that provides a visual representation helping the student to conceptualize some unfamiliar aspects of digital electronics.
        In our classification of learning tools, we make a distinction between animation used in an expositive context (to introduce theoretical concepts) and in a demonstrative context (to show how an existing device or network operate). In this paragraph we provide two examples of expositive animation. Fig. 4 shows the difference between a state and a conditioned output in a FSM by displaying the parallel evolution of ASM chart and its timing diagram. Of course, a better understanding of this tool can be gained by running the working example.
        The timing of all the animated features present in the courseware is controlled by the learner, because our experience has shown that a free running animation is often refused by the student that does not like to be paced externally. Therefore each animation is divided into steps that are controlled by the learner with the possibility of stopping or repeating the process or part of it.
        This last feature is exemplified better in Fig. 5, representing a typical microprocessor output operation. The animation explains address decoding and data transfer to the output register. It is useful to provide a few words of explanation for the buttons present on the screen. The blue ones belong to the graphical interface adopted through the courseware and their function are standard (navigation and help). The "camera" button on the bottom right starts the animation: each step not only modifies the image, but also generates an explanation window, that contains the green buttons allowing navigation inside the animation itself. The timing diagram button on the left of the "camera" shows a time domain representation of the process (working example).

Figure 2

Fig. 2. An example of a typical hypertext page.

Figure 3

Fig. 3. A hypertext page including a simple learning tool.

Figure 4

Fig. 4. Animation explaining the difference between a state output and a conditioned output
in a FSM described by an ASM chart.

Figure 5

Fig. 5. Animation of the process of a microprocessor transferring a byte of data to an output port.

Working Examples