DDR - Double Data Rate, a bus data encoding technique where read or write data is transferred on both edges of a reference clock rather than just one (rising edge and falling edge) - this doubles the data rate.
Dead Reckoning - a technique used in robotics and vehicle navigation whereby a direction or motion or rotation is selected and executed at a constant rate for a calculated period of time in order to produce a desired amount of translation or rotation to reach a target - e.g. a vehicle might be pointed north and drive at 5 feet per second for 1 hour in order to get to a target city due north of a starting point south of this target. The major disadvantage of dead reckoning is that there is no mid-course correction possible and overshoot and undershoot are also likely.
Deadline - a time relative to a request for service when the service must be completed to realize full utility of the service.
Deadline Montonic - a real-time theory directly related to RM, but with a policy such that shortest deadline receives highest priority (rather than shortest period) and a feasibility test based on deadlines rather than periods.