Deadlock - a multi-thread condition where 2 or more threads of execution are waiting on resources held by another and the graph of wait-for associations is circular - e.g. if A is waiting on resource R1 to produce resource R2; and B is waiting on resource R2 to produce resource R1 - this is a deadlock.
Decoder - a digital device which takes a bit-encoded input and produces an analog actuator output - e.g. audio playback decoder which drives a speaker.
Delayed Task - the state of a VxWorks task which has been programmed arbitrarily to yield the CPU for a period of time before replacing itself back on the ready queue - e.g. taskDelay is called.
DFD - Data Flow Diagram, a diagram used in Structured Analysis/Design which indicates where data in the system originates, how it is processed, and where it terminates (from data source to data sink).
Digital Control - feedback control where the control law is driven by discrete periodic sensor samples and based upon a Z-transform (rather than a Laplace transform in analog control).