UNIBUS is the name given to the single bus structure of the PDP-11. The processor, memory, and all peripheral devices share the same high-speed bus. The UNIBUS enables the processor to view peripheral devices as active memory locations which perform special functions. Peripherals can thus be addressed as memory. In other words, memory reference instructions can operate directly on control, status, or data registers in peripheral devices. Data transfers from input to output devices can bypass the processor completely.