Practice English vocabulary for real-time system requirements: hard vs soft real-time, WCET analysis, deadlines, and jitter.
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What is 'hard real-time' in embedded systems?
In hard real-time systems (e.g., airbag controllers, pacemakers), missing even one deadline is catastrophic. The system must guarantee that all tasks complete within their deadlines under any conditions.
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What is 'soft real-time' and what distinguishes it from hard real-time?
Soft real-time systems (e.g., video streaming, audio playback) tolerate occasional deadline misses — the result is degraded quality (dropped frame, audio glitch) but not catastrophic failure.
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What is 'WCET' (Worst-Case Execution Time) analysis?
WCET analysis calculates the upper bound on how long a task can take. This is essential for real-time scheduling — the scheduler must know the worst case to guarantee deadlines are never missed.
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A spec says 'the task has a 10ms deadline'. What does this mean for the scheduler?
A 10ms deadline means the task must finish its execution within 10 milliseconds of its release time. The scheduler must ensure this constraint is always satisfied — it cannot be exceeded.
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What is 'jitter in periodic task execution'?
Jitter is the deviation from exact periodicity. If a task should run every 10ms but sometimes runs at 9.8ms and sometimes at 10.3ms, that variation is jitter. Low jitter is critical for control systems and signal processing.