This classroom note shows how one can use a spreadsheet in developing conceptual understanding of the decimal system of arithmetic through exploring representations of integers in non-decimal base systems. In programming a spreadsheet to execute even simple operations (usually taken for granted) such as the generation of counting numbers or finding the sum of two numbers when the base number is smaller than 10, the need for conceptualization of those operations becomes obvious. In particular, a ready-made spreadsheet provides an effective medium for prospective elementary teachers who, by experiencing and overcoming difficulties in doing a non-traditional arithmetic, become better prepared to teach the conventional place value system to young children. Likewise, prospective high school teachers can experience the use of mathematical concepts, like the logarithmic function, as tools in computing applications when developing such a spreadsheet.