A block diagram is a simple drawing that shows a system as connected functional parts. Each block represents a task or module, and the arrows show how signals, data, or control move between them. In radio and software-defined radio, this makes a complex chain of processing easier to understand than a hardware-only view.
In cyber security, block diagrams help defenders map attack surface, trust boundaries, and data flow. They are used in architecture reviews, threat modeling, and incident response to spot weak links such as exposed inputs, untrusted interfaces, or overly powerful components. Attackers also rely on block diagrams during reverse engineering, because a clear functional map can reveal where a protocol is parsed, where keys are handled, or where a signal is transformed. The value of the diagram is practical: it turns a hard system into a set of steps that can be inspected, tested, and hardened.