A letter in five holes
A word is made of letters. Can a card hold a letter?
Step 1 of 4
- S is the 19th letter. So S is 19.
- 19 = 16 + 2 + 1.
- Open the 16, 2 and 1 holes.
- The card reads 10011. That means S.
The rule
Yes. Give each letter a number, then put that number on the card.
A pattern is one way of opening and shutting the holes. Four holes give 16 patterns. Five holes give 32. So 26 letters need five holes.
Our card code is invented for this lesson. A is 1, B is 2, and so on. Z is 26. Real machines use other agreed codes.
| Letter | Its number | Card |
|---|---|---|
| C | 3 | 00011 |
| S | 19 | 10011 |
| V | 22 | 10110 |
Four holes reach only 15, so they cannot hold V. Five holes reach 31.
Six patterns carry no letter: 00000 and the numbers 27 to 31.
Read the card. Pick its letter.
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