The PDA is another useful device for system control in virtual environments. In addition, the PDA is also useful in a multi-user context for instructor/learner sessions and for the differentation of private and public data. It also allows hybrid interaction and it is used as an input/output tool. As a personal device the PDA allows us to take advantage of the fact that users are familiar with the device and have already learned the interface paradigm outside of our environment. This reduces barriers for new or infrequent users to join an instructor/learner session.