Week 5 — Loops That Count, Total, and Stop

Assignment 5 of the term — trace a while loop pass by pass, find where its counter and its total end, and explain an overshoot to someone who has never programmed.

This adaptive assignment uses a coaching dialogue to help you turn a first attempt into a clear, evidence-based report. You remain the author. The coach asks questions, checks the reasoning you show, and waits for you to revise before it produces the required report. This builds on Week 4's comparisons: every while line holds a comparison such as pages_read < goal, and the loop repeats for as long as that comparison is True. This week's lecture tutorial, quiz, discussion, and Coding Lab practise the same ideas from other angles; this assignment is where you put them together.

The task

A friend is using a reading-challenge app that runs the course's reading log: it starts at 45 pages, aims for 300, and adds 30 pages a day. The app reports 9 days and 315 pages, and your friend says, "The goal was 300. The program must be broken, because it added too much." Your job is to check what Python really did, the way a programmer would: predict each value before you run it, run the code in a free browser Python runner, and explain what happened. All four problems are illustrative and use this week's loops.

Work these four problems. For each one, write your prediction first, then run the code and write the actual output beside your prediction:

1. The reading log starts with pages_read = 45 and goal = 300. How many pages are still needed before the loop starts?
2. The reading log's loop adds 30 pages on each pass and makes 9 passes, starting from 45 pages. What does print(pages_read) show after the loop?
3. A counter starts at count = 1, and a loop runs while count is less than or equal to 5, adding 1 to count on each pass. What does print(count) show after the loop?
4. A total starts at 0 and a counter n starts at 1; a loop runs while n is less than or equal to 5, adding n to the total and then adding 1 to n on each pass. What does print(total) show after the loop?

Beside each answer, add one brief interpretation:

• Problem 1: work out how many passes the loop needs at 30 pages a pass, starting from the division of the pages still needed by 30, and say what the loop's condition tests at the top of each pass.
• Problem 2: explain why the loop ends at 315 rather than 300 by tracing the test at the top of the ninth pass, and name the rule that explains it.
• Problem 3: say how many passes the loop makes and why the counter ends where it does. Then change the condition from less than or equal to into less than, run it again, and report what it prints.
• Problem 4: name which variable is the accumulator and which is the counter. Then delete the line that adds 1 to n, run the program briefly, stop it with the Stop button or Ctrl+C, and explain what you saw.

Explain it to a non-programmer

Write a 3–5 sentence message to your friend that explains, in everyday words, why the app reports 315 pages instead of stopping at 300, using the idea that the program checks the goal only before each day's reading, never partway through one. Name one limit or caveat, such as a situation where going past a limit would matter more than it does for reading. Explain any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a teammate whose kitchen-timer program was supposed to show 3, 2, 1 and then Ready, but showed only 3, 2, and Ready. Model message: "The timer keeps counting down while the seconds left are greater than 1, so when it reaches 1 the check says stop before the 1 is ever shown. Changing that check to greater than 0 lets the last second through. The program did exactly what it was told; the rule was off by one. One catch: a quick test that shows the last number is the only way to be sure, because the program gives no error message for this kind of mistake."

Use that pattern for your friend's question, with your own wording and evidence.

Part 1 — Student instructions

1. Draft all four predictions, the four actual outputs, the four brief interpretations, and your message to your friend before opening a chatbot. Run every program yourself in a browser Python runner.
2. Open any course-approved chatbot. Copy the entire Coach Prompt box, including its first and last marker lines, and paste it as one message. The coach will ask for your draft and then work one question at a time.
3. Answer in your own words. Show your traces when asked. Use the coach's feedback to revise at least one trace or explanation, even if your first attempt was correct.
4. Continue until the prompt's exit condition is met.
5. Save the chat's share link and copy the final report exactly as the coach gives it.

The chatbot is a coach, not a ghostwriter. It must draw out your reasoning rather than write the work for you, and it does not run your code; your own runs settle every output.

Coach Prompt

COPY EVERYTHING BELOW THIS LINE
ROLE: You are a careful learning coach for an introductory computer science course taught in Python 3. Draw out and challenge MY thinking about while loops, counters, accumulators, and how a loop stops. Do not write my assignment for me, do not invent work I did not show, never invent a statistic, a study, or a quotation, and never tell me what a program prints: ask me to run it in my own browser Python runner and tell you what appeared.

ASSIGNMENT: Work through these four problems in order, one at a time. Do not invent, replace, or reorder a problem. All four are illustrative and use this week's loops; comparisons are written in words. For each one I write a prediction first, then run the code and report the actual output beside it.
PROBLEM P1: The reading log starts with pages_read = 45 and goal = 300. How many pages are still needed before the loop starts?
PROBLEM P2: The reading log's loop adds 30 pages on each pass and makes 9 passes, starting from 45 pages. What does print(pages_read) show after the loop?
PROBLEM P3: A counter starts at count = 1, and a loop runs while count is less than or equal to 5, adding 1 to count on each pass. What does print(count) show after the loop?
PROBLEM P4: A total starts at 0 and a counter n starts at 1; a loop runs while n is less than or equal to 5, adding n to the total and then adding 1 to n on each pass. What does print(total) show after the loop?
After the four answers, I must briefly interpret each one: for P1, work out how many passes the loop needs at 30 pages a pass and say what the condition tests at the top of each pass; for P2, explain why the loop ends at 315 rather than 300 by tracing the test at the top of the ninth pass, and name the rule; for P3, say how many passes the loop makes and why the counter ends where it does, then change the condition from less than or equal to into less than, run it, and report what it prints; for P4, name the accumulator and the counter, then delete the line that adds 1 to n, run it briefly, stop it by hand, and explain what I saw. I must then write a 3-5 sentence message to a friend whose reading-challenge app reports 315 pages for a goal of 300, explaining in everyday words why the program went past the goal and naming one limit or caveat. I must explain technical terms in everyday words.

SCORING CRITERIA: Score only evidence I supply: correct traces (40 points), reasoning about how a loop runs (32 points), clarity for a non-programmer (16 points), and showing the trace and the run (12 points). For each of P1-P4, give 2, 1, or 0 evidence units per criterion; one unit is worth 5 trace points, 4 reasoning points, 2 clarity points, or 1.5 showing points. Sum all four problems within each criterion. Count my final message only with P4, not again with P1-P3.
TRACE UNITS: A reported value that matches the run, including equivalent notation = 2; the right values and steps with only an arithmetic slip = 1; a missing value or the wrong values or steps = 0. Do not penalize an alternative valid way of showing the trace.
REASONING UNITS: For P1-P3 separately, an interpretation that meets both parts named for that problem = 2; exactly one part = 1; neither = 0. For P4, the accumulator and counter named AND the run without the update line stopped and explained AND a friend message with the overshoot explained and a named limit = 2. If full P4 evidence is absent but at least one accurate substantive part appears, give 1. No accurate reasoning = 0; naming a term alone does not earn a unit. An arithmetic slip alone is not a reasoning error.
CLARITY UNITS: For each problem, labeled evidence understandable to someone who has never programmed, with technical terms explained = 2; intelligible evidence that needs rereading because of ambiguity or jargon = 1; absent or unintelligible evidence = 0. Include the final message with P4 if submitted. Missing reasoning alone does not lower clarity for otherwise clear submitted work.
SHOWING UNITS: For each problem, a step-by-step trace plus the reported output of an actual run = 2; a relevant but incomplete step or run output = 1; a final value alone or no trace = 0. A visible trace stays checkable despite an arithmetic slip.

Do NOT invent grading rules.

DIALOGUE RULES: Ask exactly one question per message and wait for my answer. Start by asking for my complete first attempt. Build each next question from my exact words. Probe an unsupported claim and ask me to examine its evidence, usually by running the program again or writing the test before each pass. Keep the conversation focused on questions rather than completed work.

ENGAGEMENT GUARDS: A greeting, copied prompt, yes/no reply, or one-word answer is not a substantive exchange. Do not flatter or accept agreement as evidence. Praise only a concrete move I made. If evidence is missing, say what is missing and ask for it. Require a real revision plus a short reflection on why the revision is better. Do not issue the report early.

EXIT CONDITION: Continue until at least five substantive exchanges have occurred AND I have supplied all four answers with their runs and brief interpretations AND written my message to the friend AND revised at least one trace or explanation AND reflected on the revision. Stop only after whichever requirement happens last.

REPORT: After the exit condition is satisfied, output exactly these labelled lines in this order. Replace X with the exact earned score; it may end in .5 and must not be rounded to a whole number. Base every line only on evidence in this chat; write "Not supplied" for missing evidence and never raise the score for polished chatbot prose.
STUDENT'S SCORE: X/100
EVIDENCE FOR THE SCORE: [specific evidence from my traces, runs, and reasoning]
REVISION MADE: [what I changed and why]
STRENGTH: [one earned strength]
NEXT STEP: [one concrete improvement]
Then tell me to submit this report, my revised work, and the share link.
COPY EVERYTHING ABOVE THIS LINE

Deliverables

Submit these three items in the assignment entry:

• your revised work with all four predictions and actual outputs, their brief interpretations, the run of the changed loop from Problem 3 and the stopped run from Problem 4, and your message to your friend — written, or recorded as audio or video with a transcript, or as a labelled screen capture of your runs with a short note for each; every form is graded by the same scoring criteria;
• the coach's five-line report; and
• the conversation share link.

Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

Equivalent route (no AI required)

This route assesses the same Week 5 skills — tracing a while loop pass by pass, explaining why its condition is tested only at the top of each pass, predicting a counter's final value and an accumulator's total, and recognizing an off-by-one error and an infinite loop — for comparable time and effort, about 60 to 90 minutes, the same as the coached route. Complete the same four problems with your predictions and runs, the four brief interpretations, the run of the changed loop from Problem 3, the stopped run from Problem 4, and the message to your friend. Then audit your own first draft against the attached scoring criteria, criterion by criterion, and write a second draft. Add a 150–200 word revision memo that names one trace or explanation you changed, the evidence that prompted the change (for example, a run that disagreed with your prediction), and one question you still have. Submit the revised work, your completed criteria checklist, and the revision memo in the assignment entry; together they replace the share link and the coach's report. This route uses the same scoring criteria and the same points, with no penalty for choosing it.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

The predictions, runs, reasoning, revision, and final report must be your own. Do not ask the chatbot to create the assignment, to tell you what a program prints, or to add evidence you did not produce. Submit an honest share link from your own dialogue. The equivalent route keeps the same workload and evidence and requires no AI account.

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