Real-Time Systems

A real-time system is a computing system where the correctness of an operation depends not only on its logical result but also on the time at which that result is produced. As a fundamental component in modern control systems, this branch of computer science focuses on designing hardware and software that can guarantee a response to an external event within a strict, predetermined time constraint, or "deadline." These systems are classified as either "hard real-time," where missing a deadline causes a catastrophic system failure (e.g., an automotive airbag deployment), or "soft real-time," where a missed deadline degrades performance but is not critical (e.g., a slight lag in a video stream). The core challenge is to ensure predictable, deterministic timing to reliably interact with and manage physical processes, making them essential for applications in robotics, aerospace, industrial automation, and medical devices.

1. Fundamentals of Real-Time Systems
   1. Core Concepts
      1. Definition of Real-Time Systems
      2. The Role of Time and Timeliness
      3. Logical vs. Temporal Correctness
         1. Logical Correctness
         2. Temporal Correctness
         3. Relationship Between Both Types
      4. Events and Responses
         1. Event Types
            1. External Events
            2. Internal Events
            3. Periodic Events
            4. Aperiodic Events
         2. Response Mechanisms
            1. Interrupt-Driven Responses
            2. Polling-Based Responses
            3. Event-Driven Responses
      5. Timing Constraints
         1. Importance of Timing Constraints
         2. Sources of Timing Constraints
         3. Consequences of Missed Deadlines
      6. Deadlines
         1. Hard Deadlines
         2. Soft Deadlines
         3. Firm Deadlines
         4. Mixed Deadline Systems
   2. Classification of Real-Time Systems
      1. Hard Real-Time Systems
         1. Characteristics
         2. Safety-Critical Requirements
         3. Application Examples
      2. Firm Real-Time Systems
         1. Characteristics
         2. Quality Degradation Aspects
         3. Application Examples
      3. Soft Real-Time Systems
         1. Characteristics
         2. Performance Degradation Tolerance
         3. Application Examples
      4. Mixed-Criticality Systems
         1. Multiple Criticality Levels
         2. Resource Sharing Challenges
   3. Key System Characteristics
      1. Determinism
         1. Definition and Importance
         2. Deterministic Behavior in Systems
         3. Sources of Non-Determinism
      2. Predictability
         1. Predictable Timing Behavior
         2. Factors Affecting Predictability
         3. Design for Predictability
      3. Reliability
         1. System Reliability Requirements
         2. Reliability Metrics
         3. Mean Time Between Failures
      4. Fault Tolerance
         1. Fault Types
            1. Transient Faults
            2. Permanent Faults
            3. Intermittent Faults
         2. Fault Tolerance Strategies
            1. Fault Prevention
            2. Fault Detection
            3. Fault Recovery
   4. Common Misconceptions
      1. Real-Time vs. Fast Computing
         1. Speed vs. Predictability
         2. Performance Metrics Differences
      2. Real-Time vs. General-Purpose Computing
         1. Differences in Design Goals
         2. Resource Management Approaches
   5. Typical Application Domains
      1. Aerospace and Avionics
         1. Flight Control Systems
         2. Navigation Systems
         3. Communication Systems
      2. Automotive Systems
         1. Engine Control Units
         2. Advanced Driver Assistance Systems
         3. Autonomous Vehicle Systems
      3. Industrial Automation and Control
         1. Process Control
         2. Robotics in Manufacturing
         3. Supervisory Control Systems
      4. Medical Devices
         1. Patient Monitoring Systems
         2. Infusion Pumps
         3. Life Support Systems
      5. Robotics
         1. Autonomous Robots
         2. Industrial Robots
         3. Service Robots
      6. Telecommunications
         1. Network Switches
         2. Real-Time Voice and Video
         3. Base Station Controllers
      7. Consumer Electronics
         1. Gaming Systems
         2. Multimedia Systems
         3. Smart Home Devices