Three-bit message strips
Encode and decode a short message with fixed-width three-bit groups.
Adult planning suggestion: about 9–12 · Logic & rule checking · Cooperation & communication · Language & storytelling
- Players
- Pairs or teams of three
- Time
- 12–18 minutes
- Materials and quantities
- Per team: one eight-symbol lookup table, message strip and pencil; cover the original message during decoding.
30 pupils: ten teams of three, sender, receiver and table checker; rotate after one message.
Prepare
English lookup is A=000, B=001, C=010, D=011, E=100, F=101, G=110, H=111. Chinese uses 日、月、山、水、火、木、田、人 in that same code order. Keep one language table throughout a round; the two symbol sets are not word-for-word translations.
Play
Sender chooses a message using only the eight symbols, writes exactly three bits per symbol and separates groups with spaces. Receiver covers the original and decodes each group using the same table. Preserve leading zeros: 001 is one complete code, not just the digit 1.
Example
English BAD becomes 001 000 011. Chinese 山水木 becomes 010 011 101. The strings 01 or 0001 have the wrong group length and must be checked with the sender rather than silently guessed.
Finish
Compare decoded symbols with the sender’s original, then swap roles for a new three-symbol message. Success means exact recovery and an explanation of the grouping. This public code is a representation exercise, not encryption or a secure way to share private information.
Adapt
Begin with two symbols and keep code groups in separate large boxes. Adult reads the table; a partner may copy bits. For an error, check table choice, bit order and spacing before blaming memory or speed.
Aim: Encode and decode a short message with fixed-width three-bit groups.
Practice within this activity: Using a fixed lookup, preserving leading zeros and checking communication against an original.
Adult observation: Ask why removing a leading zero changes a valid three-bit group into an invalid-length group.
Mechanism and adaptation: Our version uses fixed-width binary symbol representation. Examples and print materials are separately written; the earliest inventor is not established here.
Reference checked 24 October 2026: CS Unplugged · How binary digits work — Teaching background for binary representation. Our eight-symbol lookup, messages and three-role exercise are separately written; no original-origin or tested-effects claim.
Goals describe observable activity choices, not measured long-term gains or institutional endorsement.
Free alternatives: Draw 000–111 beside eight chosen symbols on reused paper; leave spaces between groups.
Buying recommendations reserved; no purchase required.
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.
Player shared lookup table
| Symbol | Three bits |
|---|---|
| A | 000 |
| B | 001 |
| C | 010 |
| D | 011 |
| E | 100 |
| F | 101 |
| G | 110 |
| H | 111 |
Keep each three-bit group in order, including leading zeros. Public lookup is not secret encryption.
Player encode/decode strip
| Task | Input | Output |
|---|---|---|
| Encode | BAD | ________________ |
| Decode | 010 000 001 | ________________ |
| Sender original | Code groups | Receiver recovery |
|---|---|---|
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
Teacher instructions and checked example · separate
30 pupils: ten teams of three, sender, receiver and table checker; rotate after one message.
Per team: one eight-symbol lookup table, message strip and pencil; cover the original message during decoding.
Draw 000–111 beside eight chosen symbols on reused paper; leave spaces between groups.
Print only the relevant player pages; keep this teacher page separate. Read the full web rules before leading. A helper may write or move pieces, and anyone may pause or pass. No classroom or physical-printer trial is claimed.
Encode BAD = 001 000 011. Decode 010 000 001 = CAB. Read left to right; 001 is not shortened to 1.