The use of spreadsheets in industry is widespread. Their outcomes are often used to substantiate critical business decisions. Unfortunately, spreadsheets are also error-prone. Consequently, companies risk making decisions based on inaccurate information, which eventually could lead to loss of money and reputation.
This dissertation investigates to what extent a visual language could support professional spreadsheet users in interacting with complex formulas. We divided our research into two phases. In the first phase, we try to understand better how spreadsheets are used in three ways...

Learning to program is not a easy task, as has become evident from the abundance of research papers concerning the subject. One of the learning barriers of learning a new programming language is understanding their error message, as coding errors have to be resolved before the programmer can run the code or add new functionality to the program. If the error message does not give the (kind of) information the programmer needs or uses terminology the programmer does not understand, it becomes a lot harder to fix the error it is reporting.
This thesis aimed to enhance the understanding about why the error messages of the Python programming language fail to be understood by novice programmers. An experiment was performed where novice programmers constructed how they thought the error messages should look like when encountering errors often made by novice programmers. This thesis also introduces the Error Message Component Framework, a framework which can be used to determine the different components of information an error message contains and the structure of these components. This framework was used to compare the original error message to the custom error messages created by the participants of the experiment, to investigate if the original message matched the novice programmer's information expectations.
This thesis concludes that even though some errors are often made by novice programmers, their resulting error messages may not targeted towards this group based on the terms used in these messages, the component of information these messages contains and the lack of precision of the information.

As the modern world progressing towards digital technologies, there is an increasing need for school students to learn programming skills so that they fit into the labor market now and in the future. Tangible programming toys and block-based languages are popular among younger children to learn to code. Students in middle and high school in several countries have begun to learn textual programming education as a step towards successful careers and educational opportunities. However, due to the visual nature of these materials and tools, they are inaccessible to blind students. Also, the accessibility aids used for interacting with computers in the first place are not accessible when it comes to programming. Braille displays are not accessible by most blind users as the braille literacy rates are falling, while screen readers do not read source code. Also, attempts to teach code using screen readers despite challenges kills the student’s enthusiasm. The project proposes a design approach to multi-modal human-computer interaction to reduce sensory and cognitive overload to enhance learning outcomes for this user group. The design goal was to develop an affordable audio-tactile interface, to help blind high school students to learn textual programming languages. Research insights were gathered from literature research, surveys, interviews, observation studies, and co-creation sessions with blind students. The insights were synthesized to form ideas, and concepts were explored. The final concept was then taken to a level of functional prototype and was validated in simulated tests. A sustainable business model was also developed to take the project forward as an open-source hardware venture.