Features of real-time systems:
- Determinism:?Real-time systems must be deterministic, which means that the system's behavior must be predictable and repeatable for a given input. This ensures that the system will always meet its deadlines, regardless of the load or other factors.
- Timing constraints:?Real-time systems must meet timing constraints, which are deadlines that must be met in order for the system to function correctly. For example, a traffic light system must be able to change the light colors within a specified time period in order to keep traffic flowing smoothly.
- Reliability:?Real-time systems must be reliable, which means that they must be able to meet their deadlines even in the event of failures or unexpected events. This is critical for systems that are safety-critical, such as air traffic control systems.
- Scalability:?Real-time systems must be scalable, which means that they must be able to handle increasing loads without sacrificing performance or reliability. This is important for systems that are expected to grow in size or complexity over time.
- Security:?Real-time systems must be secure, which means that they must be protected from unauthorized access or modification. This is important for systems that handle sensitive data, such as financial systems.
- Periodicity:?Real-time systems often have periodic tasks, which are tasks that must be executed at regular intervals. For example, a traffic light system may have a task that checks the traffic every 10 seconds.
- Deadlines:?Real-time systems must meet deadlines, which are time limits that must be met for certain tasks. For example, an air traffic control system may have a deadline of 5 seconds for responding to a change in the airspace.
- Priority:?Real-time systems often have priority-based scheduling, which means that tasks are executed in order of priority. High-priority tasks are executed before low-priority tasks.
- Resilience:?Real-time systems must be resilient to failures, which means that the system must be able to continue operating even if some components fail. For example, a factory automation system may have redundant components in case one of the components fails.
- Safety:?Real-time systems must be safe, which means that the system must not cause any harm to people or property. For example, an air traffic control system must be safe to use, even in the event of a failure.
- Fault tolerance:?Real-time systems must be fault tolerant, which means that the system must be able to continue operating even if some of its components fail. The system must have redundant components and must be able to detect and recover from failures quickly.
- Performance:?Real-time systems must be able to meet their deadlines in a timely manner. The system must be able to process data and generate output quickly enough to meet the deadlines.
?Architecture styles for real-time systems:
- Real-time embedded systems:?These systems are designed to respond to events within a specified time period. For example, a traffic light system needs to respond to changes in traffic within milliseconds in order to keep traffic flowing smoothly.
- Distributed real-time systems:?These systems are composed of multiple components that are located on different computers. The components need to be able to communicate with each other and coordinate their activities in order to meet the real-time requirements of the system.
- Hybrid real-time systems:?These systems combine elements of both real-time and non-real-time systems. For example, a factory automation system may have some components that need to respond to events within milliseconds, while other components can have looser deadlines.
- Hard real-time systems:?These systems have strict deadlines that must be met in order to ensure the safety or correctness of the system. For example, an air traffic control system must be able to respond to changes in the airspace within milliseconds in order to prevent collisions.
- Soft real-time systems:?These systems have deadlines that are not as strict as hard real-time systems. For example, a video game may have a deadline of 30 frames per second, but it is not critical if the frames are not rendered exactly on time.
The best software architecture style for a particular real-time system will depend on a number of factors, such as the criticality of the system, the performance requirements of the system, and the budget for the system.
The components of a real-time system can be classified into hardware and software components.
Hardware components of a real-time system include:
- Processor:?The processor is the central processing unit of the system. It is responsible for executing the code and performing the calculations required by the system.
- Memory:?The memory is used to store data and instructions. The real-time system must have enough memory to store the code, data, and buffers required to meet the deadlines.
- I/O devices:?The I/O devices are used to interact with the outside world. The real-time system must have I/O devices that can meet the deadlines required by the system.
- Communication network:?If the real-time system is distributed, it must have a communication network to connect the different components of the system. The communication network must be able to meet the deadlines required by the system.
Software components of a real-time system include:
- Operating system:?The operating system is responsible for managing the resources of the system, such as the processor, memory, and I/O devices. The operating system must be able to ensure that the system meets its deadlines.
- Real-time kernel:?The real-time kernel is a specialized operating system kernel that is designed to meet the requirements of real-time systems. The real-time kernel must be able to schedule tasks and manage resources in a way that ensures that the system meets its deadlines.
- Application software:?The application software is the software that is specific to the application that the real-time system is used for. The application software must be designed to meet the real-time requirements of the system.
These are just some of the components of a real-time system. The specific components that are used in a particular real-time system will depend on the application and the environment in which the system will be used.
