In the PCBuildAR project, the principles from the 3C model and the potential of mobile AR cards are now being brought together. How this can look like is now described by means of each C.
4.1 Content and AR
Each PCBuildAR card shows a component of a classic computer system as a 2D representation. Currently, eight cards for eight different components and several variations of the components are produced (see Fig. 1). Variations are needed because later tasks require the exchange of components to solve a problem, e.g. upgrading a classic home computer for professional photo or video editing. Using a mobile device, tablet or smartphone, these images can be scanned with the camera and the additional information stored on them becomes visible. Declarative knowledge, e.g. the function, is conveyed for each component that is to be used afterwards (see Sect. 4.2). Because of the definition in [7, 8], AR cannot be considered as a single medium but as multimedia. Therefore, learning materials with AR have to take into account the principles from the Cognitive Theory of Multimedia Learning (CTML), so that learners are not cognitively overstrained, but are supported in their learning processes . For our AR cards, this means that 3D visualizations are not supplemented by written texts but by auditory information according to the modality principle. We also dispense with redundant representations by assigning AR a clear function, namely the extension of the physical card, which remains visible and thus relevant .
4.2 Construction and AR
Within the PCBuildAR project, experienced computer science teachers formulate the problem-based tasks according to technical issues. Examples include upgrading the computer so that professional video editing software can run without crashes or preparing the computer for graphically demanding computer games. With the latter task we also want to consider real problems from the current living environment of many children and young people. These tasks can be solved by first folding the cards correctly and then replacing the corresponding component. Afterwards the cards are scanned with a mobile device and the learners get feedback on the display if an appropriate solution for the problem has been found.
AR also serves here as a support system, as the information on the components can be made visible through scanning the markers, if needed. Especially beginners can benefit from such support actions as just-in-time information [10, 11].
4.3 Communication and AR
The communication component of our AR card is also linked to the tasks. If the cards are used in cooperative learning settings, the exchange between learners takes place. In the classroom, the teacher can also be called upon to provide support if necessary.
The tasks that are to be solved in a team require the exchange of information between the learners. Basically, this component should be able to be implemented according to the ideas or conceptions of the respective teachers. We do not want to impose too many restrictions here (see Fig. 2).