Round-robin time slices
Allocate repeated two-unit turns and track unfinished work in a queue.
Adult planning suggestion: about 9–12 · Logic & rule checking
- Players
- 3 per group
- Time
- 20–30 minutes
- Materials
- Printed record sheet, pencil and paper markers
Prepare
All jobs arrive at time 0 in order A,B,C and require 5,3,1 work units. Use quantum 2 and zero switching overhead. The queue initially[A,B,C]. No jobs arrive later and there is no waiting for input.
Follow the rule
Take the head job. Run it for the smaller of 2 and its remaining work. Advance the clock by that actual amount. If finished, record completion time and remove it; otherwise append it to the queue tail.
Check each step
Use three roles: scheduler moves the queue, worker subtracts remaining work, auditor verifies clock intervals. Do not award an unused part of a short final slice to the same finished job.
Worked example
Trace A0–2,B2–4,C4–5,A5–7,B7–8,A8–9. C completes at 5,B at 8,A at 9. Total elapsed 9 equals the initial 5+3+1; no idle time was specified.
Finish and adapt
After checking the full trace, repeat with quantum 1 and compare completion times without declaring one universally best. With quantum 1,C completes at 3,B at 7,A at 9. Age/support are planning suggestions; this is a scheduling exercise, not real multitasking software.
Purpose, observation and provenance
Within this activity: Allocate repeated two-unit turns and track unfinished work in a queue.
Observe whether unfinished jobs go to the tail and short slices advance by actual work.
Our rules, examples and printable diagrams are separately prepared. The earliest inventor of the broader mechanism is not established here.
OSTEP: CPU scheduling — Technical background, not an evaluated primary-school lesson. This paper exercise and examples are our adaptation; age and support are adult planning suggestions.
Secondary practice: Cooperation and explaining a check.
For a class of 30, use ten groups of three. Prepare one player-material set per group and keep the host key with the adult. Rotate operator, recorder and checker after each worked example; a reader or scribe may help without choosing answers. Avoid public ranking or diagnostic labels.
Age bands are planning suggestions. Background references may address older learners and do not validate suitability for this age band. Goals describe observable actions, not measured long-term gains or institutional endorsement.
Free alternative: Copy the supplied grids, labels and cards onto reused paper. No specialist product is needed. Adults may prepare pieces or act as a scribe.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. This is a manual tabletop kit, not an online opponent, automatic judge or solver.
Round-robin time slices · Player sheet
Before you begin
- All jobs arrive at time 0 in order A,B,C and require 5,3,1 work units. Use quantum 2 and zero switching overhead. The queue initially[A,B,C]. No jobs arrive later and there is no waiting for input.
- Take the head job. Run it for the smaller of 2 and its remaining work. Advance the clock by that actual amount. If finished, record completion time and remove it; otherwise append it to the queue tail.
- Use three roles: scheduler moves the queue, worker subtracts remaining work, auditor verifies clock intervals. Do not award an unused part of a short final slice to the same finished job.
| Job | Arrival | Work |
|---|---|---|
| A | 0 | 5 |
| B | 0 | 3 |
| C | 0 | 1 |
Quantum2; no switch cost.
| Job | Time interval | Remaining / queue |
|---|---|---|
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
Round-robin time slices · Host key — keep separate
q 2: C5,B8,A9. q 1: C3,B7,A9. Both finish all work by 9.
What to observe
Observe whether unfinished jobs go to the tail and short slices advance by actual work.
Use the three-person roles described in the rules; offer reading or writing support without selecting answers.
Read the rules as well as this example. Other valid solutions may exist for the puzzle boards. This key is not a claim of uniqueness or measured learning gains.
| Constraint / action | Evidence / correction |
|---|---|
| ________ | ________ |
| ________ | ________ |
| ________ | ________ |
| ________ | ________ |