1. 1 1 7-Dec-15 Binary Converting to and from decimal

2. 2 2 7-Dec-15 Decimal We normally use the decimal (denary) system, also called base 10 There are 10 different symbols (digits) 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 To count higher than nine we re-use the symbols by putting them in columns The value of a symbol depends on its position

3. 3 3 7-Dec-15 Decimal positions 1000100101 ThousandsHundredsTensUnits 8253 Eight thousand two hundred and fifty three

4. 4 4 7-Dec-15 Binary Computers use the binary system, also called base 2 There are two different symbols (digits) 0, 1 To count higher than one we re-use the symbols by putting them in columns The value of a symbol depends on its position

5. 5 5 7-Dec-15 Binary positions 8421 EightsFoursTwosUnits 1101 One eight, one four, no twos and one unit That makes thirteen

6. 6 6 7-Dec-15 Counting in binary and decimal 0010008 1110019 102101010 113101111 1004110012 1015110113 1106111014 1117111115

7. 7 7 7-Dec-15 Why do computers use binary? Computer components that store or handle data are often two-state devices This is like a switch that can be on or off A memory unit could exist in two voltage states, high or low A voltage on a cable could be high or low A light could be on or off Two states can be coded by binary 0 and 1

8. 8 8 7-Dec-15 Why am I learning about binary? In your Cisco course, you will learn about IP addresses and how to split up a network into subnets You need to work out subnet addresses and workstation addresses For this you need to use binary

9. 9 9 7-Dec-15 Bytes or octets We often handle binary digits (bits) in groups of eight Sometimes these groups are called bytes Sometimes they are called octets We shall often be calling them octets Examples of octets: 00101101 10110010

10. 10 7-Dec-15 Convert binary to decimal Value1286432168421 Binary Convert 11001010 binary to decimal Write in the binary digits under their values

11. 11 7-Dec-15 Convert binary to decimal Value1286432168421 Binary11001010 Convert 11001010 binary to decimal Write in the binary digits under their values Next write in the value for each binary 1 digit

12. 12 7-Dec-15 Convert binary to decimal Value1286432168421 Binary11001010 1286482 Convert 11001010 binary to decimal Write in the binary digits under their values Next write in the value for each binary 1 digit Add up the values 128 + 64 + 8 + 2 = 202

13. 13 7-Dec-15 One for you to try Convert 10010101 from binary (base 2) to decimal (base 10) Value1286432168421 Binary

14. 14 7-Dec-15 Answer Convert 10010101 from binary (base 2) to decimal (base 10) Value1286432168421 Binary10010101 1281641 128 + 16 + 4 + 1 = 149

15. 15 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary Check Convert 185 decimal to binary Can you take 128 from 185? Yes. Put 1 under 128 What is left? 185-128 = 57

16. 16 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary1 Check We have 57 left Can you take 64 from 57? No. Put 0 under 64 What is left? Still 57

17. 17 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary10 Check We have 57 left Can you take 32 from 57? Yes. Put 1 under 32 What is left? 57 – 32 = 25

18. 18 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary101 Check We have 25 left Can you take 16 from 25? Yes. Put 1 under 16 What is left? 25 – 16 = 9

19. 19 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary1011 Check We have 9 left Can you take 8 from 9? Yes. Put 1 under 8 What is left? 9 – 8 = 1

20. 20 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary10111 Check Wwe have 1 left Can you take 4 from 1? No. Put 0 under 4 What is left? Still 1

21. 21 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary101110 Check We have 1 left Can you take 2 from 1? No. Put 0 under 2 What is left? Still 1

22. 22 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary1011100 Check We have 1 left Can you take 1 from 1? Yes. Put 1 under 1 What is left? Nothing. Finished.

23. 23 7-Dec-15 Convert 185 decimal to binary Value1286432168421 Binary10111001 Check 185 decimal is 10111001 binary

24. 24 7-Dec-15 Convert decimal to binary Value1286432168421 Binary10111001 Check128321681 Check: write in the values of the 1 digits and add them up 128 + 32 + 16 + 8 + 1 = 185 That’s the number we started with. It’s correct.

25. 25 7-Dec-15 One for you to try Convert 248 from decimal to binary Check your answer Value1286432168421 Binary Check

26. 26 7-Dec-15 Answer Convert 248 from decimal to binary Check your answer Value1286432168421 Binary11111000 Check1266432168 128 + 64 + 32 + 16 + 8 = 248 So 11111000 is correct.

27. 27 7-Dec-15 End