In interactive computing, what is the term for the time lag between pressing the last input key and seeing the first output character on the screen?

Introduction / Context:
Users perceive system performance primarily through the delay between their actions and visible results. The metric capturing the interval from the end of an input action to the first visible output is response time. Understanding this concept is essential for designing responsive user interfaces and sizing systems for interactive workloads.

Given Data / Assumptions:

• Input is typed via keyboard and the final keypress completes the request.
• Output appears on a screen (terminal, console, or GUI).
• The measure of interest is the first visible feedback, not full completion.

Concept / Approach:
Response time includes input handling, queuing, processing, and rendering the first character or visual feedback. It differs from throughput (work per unit time) and from batch turnaround time (submission to completion with no interaction). Optimizing response time often improves user satisfaction more than raw throughput for interactive tasks.

Step-by-Step Solution:

Verification / Alternative check:
Batch processing and classic turnaround time involve non-interactive jobs; they are measured from submission to completion of the whole job, not first feedback. Therefore they do not match the definition here.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing time to first byte with time to full render; users care first about initial feedback, then total completion.

Final Answer:
Response time.