I'm confused with the event and time triggered systems. The term real-time-system is always preceded by time-triggered. Is it possible an event-triggered system to be a real-time-system at the same time? Or does real-time-system term mean that the system is time-triggered?
Thanks for help
A real time system is a system with guaranteed time of execution of each action. This doesn't mean that it is as fast as possible, or that it is interactive. But it means that a computation is guaranteed to end in less than X milliseconds. So If a real-time system needs to do A and the B, one way of accomplishing this is to start A, and after X milliseconds start B. No need for A to signal that it has completed, because it is guaranteed to complete before X milliseconds have passed. This is time-triggered.
An event-triggered system is a system where an operation starts in response to an event, and the time at which the event should arrives is not known until the event happens. An event might be, for example, a keyboard or mouse event, or a message pushed to a queue.
A real-time system can have both event triggers and time triggers. For example, an event might trigger a chain of actions, but inside the chain, some actions may be triggered by timers.
For example, a smartphone camera might have real-time elements in it for reading the pixels, doing some real-time computations on them, and then transmitting them to the RAM. These operations might be controlled by a clock, this is the time-triggered part. But the whole action of taking an image is trigger by the event of a user pressing some button, so this is the event-triggered part.