How do ones and zeros become letters?

How does a computer that knows only ones and zeros read letters?

1. How does a computer that knows only ones and zeros read letters?
2. This chapter answers that one question.
3. People say there is nothing inside a computer but ones and zeros.
4. And yet letters appear on the screen.
5. Where do those letters come from?
6. Picture eight light bulbs in a row.
7. A single bulb can say only two things.
8. On, or off.
9. One bulb cannot spell anything.
10. Put eight of them side by side and that changes.
11. The number of on-off combinations gets large.
12. Now suppose a table pairs every combination with a letter.
13. The computer reads the combination and pulls the letter out of that table.
14. That table has a name: ASCII.
15. The pairing table is all the computer has.
16. Press one of the bulbs on the switchboard above.
17. Change the combination and the number changes.
18. Change the number and the letter changes.
19. Now let the numbers turn this around.
20. One bulb gives you 2 possibilities.
21. Eight in a row give you 256.
22. Add exactly one more bulb.
23. Nine bulbs give you 512.
24. One bulb more, twice as many possibilities.
25. When a place is added the count does not add up.
26. It multiplies.
27. So thirty-two bulbs give you 4,294,967,296.
28. The bulbs went up only fourfold.
29. What they can count went all the way up there.
30. The numbers you just heard are not written into the sentence.
31. They are worked out while this page renders.
32. To sum up.
33. A computer does not know letters.
34. It follows a table that pairs on-off combinations with letters.
35. Next chapter looks at the device that actually handles those combinations.
36. What exactly does a CPU do?

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