The physical characteristics of new HSIs include devices that support multimodal interaction, such as touch screens, gesture interaction, speech recognition and synthesis, haptic input and output (that is, technologies that use touch and tactile feedback to enable HSI), and even direct body-machine interfaces (sensors). Advanced display and interaction features already available and under development make use of hand­held devices, head-mounted displays, large overview displays, three-dimensional (3-D) displays (with or without glasses), motion and position tracking. To support such extensive interaction capabilities, the whole system is typically driven by high — performance numerical and graphics processors for demanding applications such as high-resolution displays and computationally intensive applications like processing and trending of large amounts of plant data. (Several of the terms mentioned above may be unfamiliar to some readers; they will be explained a later.)