Dan Bricklin conceived VisiCalc while watching a presentation at Harvard Business School. The professor was creating a financial model on a blackboard that was ruled with vertical and horizontal lines (resembling accounting paper) to create a table, and he wrote formulas and data into the cells. When the professor found an error or wanted to change a parameter, he had to erase and rewrite several sequential entries in the table. Bricklin realized that he could replicate the process on a computer using an "electronic spreadsheet" to view results of underlying formulae.