Doctor of Philosophy
The fields of Science, Technology, Engineering, and Mathematics (STEM) have been growing at an accelerating rate in recent times. Knowing how to program has become one key skill for entering all of these STEM fields. However, many students find programming difficult. The block based programming language, Scratch, was specifically designed to lower hurdles to learning how to program for sighted students. Unfortunately, although very effective and widely used in K12 classrooms, Scratch, similar to other block based languages, is inaccessible to students who are blind and visually impaired (BVI). This thesis is part of a larger project to make the Scratch environment accessible to BVI students. The focus of this thesis is on creating a tangible code block design that: 1) is accessible to BVIs, 2) retains the reduced need to struggle with syntax of Scratch, 3) allows code construction through action, 4) and co-construction with other BVI and sighted students, and 5) can create moderately sized programs at low cost.
The first several parts of this thesis consider the design and assessment process for the code blocks, which went through two iterations. The four major components of the first design iteration were: 1) the use of passive blocks, with use of 2) the local edge shape connectivity between blocks defining the program syntax, 3) telescoping tubing to allow nested expressions
when valid, and 4) haptically legible commands for both Braille and non-Braille users. The first iteration of the block design was compared to a text based method in building and correcting operator expressions that included both simple and nested expressions of the arithmetic, relational and logical operators. BVI participants produced correct code significantly more when doing the tasks with the code blocks than with the text method. Although the text method was faster, it did not account for any additional time that would be needed to identify and change incorrect code before a program could be run.
One weakness of the first iteration was that it was difficult for BVI participants to easily determine connectivity between validly connecting code blocks. The second design iteration considered the effect of embedding different degrees of magnetic attraction within the local shape connection to improve identification of the connectivity. It also considered how to represent some commands that had additional restrictions to those found with most of the other code block types. In particular, we considered the use of different “stopper” designs to prevent numeric literals from being placed in the left slot of a “set” command, which could only accept a variable. Results from a set of studies evaluating the ability of BVI participants to identify the connectivity between blocks found that the magnetic attraction within the connection significantly improved accuracy and ease of use, with the stronger magnetic connections preferred. They also found that a stopper design could be used for “exceptions”, with the longer stopper aligned with the local connection preferred.
The final part of the thesis examines the use of the code blocks by the targeted population (BVI students in middle school) in a classroom setting within the context of the entire nonvisual interface. To do this, two day code camps were conducted with BVI middle school students, and recorded on video and audio. Qualitative content analysis was used to verify that the students interacted with the system as intended by the code block design. Results suggest that the students did interact with the code blocks as intended by the design, but minor improvements should be made to increase their ease of use. Participants did appear to have a positive experience with the code blocks and the system overall.
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