Binary Without the Fear

You'll learn

• The lamp card: 1, 2, 4, 8, 16, 32, 64, 128, each lamp worth double the one to its right — the only thing to memorise
• Reading a row by adding the lit lamps (192, 10, 77, 255, 0) and writing a number by asking "can I afford it?" eight times
• Why a subnet mask can only be one of nine values, and why the prefix length is just the count of lit lamps (240 is /28, 224 is /27)
• The block size from the last lit lamp: 240 means networks of 16, 224 means networks of 32
• The bitwise AND: 77 AND 224 is 64, so the network is 192.168.1.64/27, broadcast .95, hosts .65 to .94
• The ten-second method: count the lit lamps, take the last one's value, find the multiple at or below the host
• The real thing: Windows Calculator in programmer mode as a self-check, then a real host worked through the three steps
• Exam corner: the prefix length of 255.255.255.224

Chapters

1. 0:00Thirty seconds on the clock
2. 0:43The lamp card
3. 1:23Reading a row: add the lit lamps
4. 1:53Writing a number: "can I afford it?"
5. 2:53240 into lamps
6. 3:29Masks are the easy case: the nine values
7. 4:03The slash is the count of lit lamps
8. 4:28The last lit lamp: the street width
9. 4:55The street test with the lamps: AND
10. 5:42The street .64 to .95
11. 6:04The ten-second version
12. 6:29The real names
13. 7:00The three steps
14. 7:29The real thing: the calculator, then a real host
15. 8:43Exam corner
16. 9:00Recap and next time