To realize an example of architecture, the object must be described. However, this in itself is insufficient—the process of realizing the object must itself be supported. It is in both these dimensions that computers have been of benefit in the practice of architecture in the 20th century. The use of computers in architectural design has been motivated by a number of factors and driven by others, and has come to reflect the evolution of practice through the last half of the 20th century. The work of an architect started the century relying heavily on teams of colleagues, employees, consultants, and contractors; by the close of the century, although the practice of architecture was much the same, the picture had changed to include computing tools in almost every team and every practice, drawing the participants closer together through the whole sequence of events leading to the construction of a building. As this change took place, the challenge with the use of computing tools came to b...