Real-time systems have several key characteristics that distinguish them from non-real-time systems. These include:

Real-Time Systems by Jane W. S. Liu is a foundational text in computer science that bridges the gap between theoretical scheduling and practical system implementation. Rather than a literal "story," the book tells the "life cycle" of a real-time task—from its arrival in a system to its critical need for completion before a hard deadline. Amazon.com Core Concepts and "Life of a Task"

A "soft" real-time system (video streaming) can tolerate rare missed frames. A "hard" real-time system (airbag deployment) cannot. Liu provides the formulas to calculate worst-case response time (RTA), accounting for release jitter and interrupt latency.