Templates & Runtime Inputs

So far, every prompt has been fixed text. But in real systems, prompts are usually templates. A template contains placeholders that are filled at runtime. Example: ``` Explain {{topic}} to a beginner in 3 bullet points. ``` The instruction stays the same. The input changes. At runtime: - topic = batteries - topic = solar panels - topic = HTTP The same prompt structure works for different inputs without rewriting the instruction itself. This separation between instructions and runtime data is one of the foundations of instructional engineering. You are building reusable behavioral systems, not single-use prompts. Different platforms use different placeholder syntax: - {{topic}} - {topic} - $topic The exact syntax matters less than the concept: separate the instruction from the data.