In Watson's day, his statement was not at all controversial. Computers of the time were mammoth machines. They were expensive to build and maintain, and were extremely difficult to program. These computers evolved into a type of computer called mainframes. A mainframe computer was a massive computer that could be used by many users simultaneously. Each user had her own monitor and keyboard, but there was only one main computer "brain". The processor quickly jumped from individual to individual. Each person had the impression she had the computer to herself. This illusion broke down when a large number of people were using the system or somebody was running an especially demanding process. An important advantage of this scheme was the use of the computer as a communication medium. Since a large number of people were sharing the same computer at the same time, it was not too difficult to use the computer to talk to others in the system.