Program comprehension is an important function undertaken in the process of software maintenance. Compared to other research subjects, program comprehension has received little attention even though it is one of the biggest influences on a programmer's output. Research into aiding program comprehension has led to software visualisations, but these are mainly two-dimensional views and overload the viewer with information. With the advent of more powerful computers, virtual reality can be used to create three dimensional visualisations, in which the viewer is able to navigate freely. Spreadsheets were studied in this work on visualisation because programming languages are extremely complex and a model employing spreadsheets was developed. Spreadsheets offer many similarities to programming languages, for example, cell referencing and formulas in spreadsheets are similar to procedure calls, variable referencing and data manipulation in conventional programming languages. Common mistakes made in spreadsheets have been shown to be very difficult to locate, mainly because the spreadsheet user has a reduced ability to make hypotheses about the computational domain of a spreadsheet. Therefore, in order to address this shortcoming a visualisation model was developed to allow a spreadsheet user to be able to view both the problem domain (the what) and the computational domain (the how) simultaneously. A spreadsheet, a spreadsheet description language and a virtual reality system were the objects in the model, and a generator and translator were the links between those objects. Implementing the model indicated that spreadsheets could be visualised in virtual reality, and this technique was shown to improve the process of spreadsheet comprehension
