2. The Internet Book

3. Chapter 5

4. 3 The World Was Once Digital 150 years ago, telegraph messages were sent from one town to another. –Using audible clicks to encode messages –Switching a light “on” and “off” is a similar principle

5. 4 A Telegraph Is Digital A telegraph is digital technology because data is: –Transferred by discrete clicks –Not transferred as a continuous varying signal

6. 5 Morse Code Telegraph operators used this code because it: –Represented letters and words –Used short and long clicks (dots and dashes)

7. 6 Letters And Digits In Morse Code Figure 5.1: Example of Morse code

8. 7 Users Did Not Encounter Morse Code The relevance of the telegraph to the Internet is because it: –Encoded all letters and digits using only 2 values –Used a code to transmit a message –Used an encoding scheme not encountered by customer

9. 8 Virtually Instant Communication Sending messages to far away locations was: –Accomplished without using a human courier –Allowed people to learn about events as they occurred

10. 9 Speed Is Relative The telegraph changed the world because it was so fast compared to a courier. By today’s standards communication by telegraph is slow.

11. 10 Conclusion Is it necessary to understand the binary encoding of Internet messages in order to use the Internet?

12. 11

13. 12 Glossary Binary – Any number system that uses two values. Binary digit (bit) –Either a 0 or 1. Digital – Any technology that uses numbers to represent information.