System vs User Prompts

In advanced AI interactions (and especially in the API), there is a crucial distinction between the System Message and the User Message.

1. The System Message (The Founder)

The System Message (or System Prompt) sets the "ground rules" for the entire conversation. It is the highest level of instruction.

• Purpose: Defines the AI's identity, constraints, and behavior.
• Example: "You are a helpful assistant that only responds in Markdown tables. You never use conversational filler like 'Sure, here is your table'."

2. The User Message (The Request)

The User Message is the specific task or question you are asking in the moment.

• Purpose: Provides the data or the question to be processed.
• Example: "Analyze the sales data for Q3."

graph TD
    System[System Prompt: WHO am I?] --> Context[Shared Context]
    User[User Prompt: WHAT do I do?] --> Context
    Context --> Model[LLM Logic]
    Model --> Result[Response]

3. Why the Distinction Matters

• Stability: Guidelines in the System Message are harder for the AI to "forget" or ignore than instructions buried in the User Message.
• Security: System Prompts are often used to implement "Guardrails" to prevent the AI from generating harmful content.
• Efficiency: You don't have to repeat your preferences every time if they are set in the System Prompt.

4. In the Web Interface: "Custom Instructions"

While the web chat looks like just one box, you can access the System Prompt level through Custom Instructions (in your profile settings). This allows ChatGPT to "remember" your professional background and style for every new chat.

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Hands-on: Use Custom Instructions

1. Open ChatGPT settings and find Custom Instructions (or "Personalization").
2. In the "How would you like ChatGPT to respond?" box, enter: "Always be concise and use bullet points."
3. Start a new chat and ask any question. Observe how the "System-level" instruction overrides the default chat style.

Key Takeaways

• System Prompts set the rules; User Prompts ask the questions.
• Custom Instructions are the web version of System Prompts.
• Use System Prompts for permanent constraints and behavior.