1
00:00:00,000 --> 00:00:00,500

2
00:00:00,500 --> 00:00:02,940
I remember seeing the Wizard
of Oz, and near the end

3
00:00:02,940 --> 00:00:05,070
they pull back the
curtain to reveal who

4
00:00:05,070 --> 00:00:07,080
really is acting as the wizard.

5
00:00:07,080 --> 00:00:10,500
And that's what I'd like to do
right now with IP version 4.

6
00:00:10,500 --> 00:00:14,640
Even though IP version 4, it's
represented as dotted decimal--

7
00:00:14,640 --> 00:00:17,160
here we have four
numbers right here,

8
00:00:17,160 --> 00:00:19,560
and they're separated
by three periods--

9
00:00:19,560 --> 00:00:22,410
what's really happening
is that's just for us

10
00:00:22,410 --> 00:00:24,180
humans as a convenience.

11
00:00:24,180 --> 00:00:26,310
What's really going
on behind the scenes

12
00:00:26,310 --> 00:00:28,560
is that each one
of these numbers

13
00:00:28,560 --> 00:00:31,380
represents one byte of data--

14
00:00:31,380 --> 00:00:35,230
8 bits which go into
one byte of data.

15
00:00:35,230 --> 00:00:36,330
So each of these numbers--

16
00:00:36,330 --> 00:00:39,360
130, 16, 33, and 17--

17
00:00:39,360 --> 00:00:42,750
sometimes these numbers are
referred to as an octet.

18
00:00:42,750 --> 00:00:45,390
And an octet is nothing
more than 8 bits

19
00:00:45,390 --> 00:00:48,330
that are all represented
together in the same grouping.

20
00:00:48,330 --> 00:00:51,210
So whether you want to call this
first number the first number,

21
00:00:51,210 --> 00:00:54,810
or the first bite, or the
first octet, all of those

22
00:00:54,810 --> 00:00:55,980
mean the same thing.

23
00:00:55,980 --> 00:00:58,680
Now, the great news for you
and I is that, in converting,

24
00:00:58,680 --> 00:01:01,830
if we needed to, to convert
binary to decimal or decimal

25
00:01:01,830 --> 00:01:03,600
to binary, it's really
straightforward,

26
00:01:03,600 --> 00:01:06,450
because in either method
we're going to use we're

27
00:01:06,450 --> 00:01:08,460
going to first write
out this table.

28
00:01:08,460 --> 00:01:10,200
We have a decimal
number that we're

29
00:01:10,200 --> 00:01:11,670
going to convert to binary.

30
00:01:11,670 --> 00:01:13,170
So we're going to
do that one first.

31
00:01:13,170 --> 00:01:15,030
And it's really just a game.

32
00:01:15,030 --> 00:01:17,997
And I call it the,
does it fit game.

33
00:01:17,997 --> 00:01:19,080
And here's how we play it.

34
00:01:19,080 --> 00:01:20,290
We take a number--

35
00:01:20,290 --> 00:01:22,157
so we're going to
first start with 130,

36
00:01:22,157 --> 00:01:23,490
and we're going to write it out.

37
00:01:23,490 --> 00:01:26,010
And all we need to do is
take this very first number

38
00:01:26,010 --> 00:01:28,350
on the far left, 128,
and ask ourselves

39
00:01:28,350 --> 00:01:30,000
the question, does it fit.

40
00:01:30,000 --> 00:01:32,340
Does 128 fit into 130?

41
00:01:32,340 --> 00:01:33,870
Yes or no?

42
00:01:33,870 --> 00:01:35,650
It's a binary question.

43
00:01:35,650 --> 00:01:37,140
If the answer is
yes, we're going

44
00:01:37,140 --> 00:01:39,660
to put a bit on
in that position.

45
00:01:39,660 --> 00:01:42,840
And we're also going to
subtract that value of 128

46
00:01:42,840 --> 00:01:45,060
from the number we're
trying to convert.

47
00:01:45,060 --> 00:01:47,550
So the remainder of this is 2.

48
00:01:47,550 --> 00:01:49,980
130 minus 128 is 2.

49
00:01:49,980 --> 00:01:52,740
So we take that remainder,
and we play the game again.

50
00:01:52,740 --> 00:01:55,160
Does 64 go into 2?

51
00:01:55,160 --> 00:01:55,660
No.

52
00:01:55,660 --> 00:01:58,360
Well, it might a fraction of
the time, but we're looking for,

53
00:01:58,360 --> 00:02:02,150
does that number go in an
entire time at least once?

54
00:02:02,150 --> 00:02:04,920
And if the answer is, no, it
doesn't, we put a 0 there.

55
00:02:04,920 --> 00:02:05,850
How about 32?

56
00:02:05,850 --> 00:02:07,350
Does it go into 2?

57
00:02:07,350 --> 00:02:08,055
No, it doesn't.

58
00:02:08,055 --> 00:02:08,940
So that gets a 0.

59
00:02:08,940 --> 00:02:10,380
Does 16 go in?

60
00:02:10,380 --> 00:02:11,110
No, it doesn't.

61
00:02:11,110 --> 00:02:11,970
That gets 0.

62
00:02:11,970 --> 00:02:13,500
8-- does it go into 2?

63
00:02:13,500 --> 00:02:14,100
Nope.

64
00:02:14,100 --> 00:02:15,120
How about 4?

65
00:02:15,120 --> 00:02:15,810
Nope.

66
00:02:15,810 --> 00:02:17,400
And then we get down to 2.

67
00:02:17,400 --> 00:02:19,830
Does 2 go into 2?

68
00:02:19,830 --> 00:02:21,300
And the answer is yes it does.

69
00:02:21,300 --> 00:02:23,040
It goes exactly one time.

70
00:02:23,040 --> 00:02:27,420
So we'll subtract 2 from
it, and we are down to 0.

71
00:02:27,420 --> 00:02:30,060
So the question is,
does 1 go into 0.

72
00:02:30,060 --> 00:02:31,800
And the answer is, it does not.

73
00:02:31,800 --> 00:02:34,290
And so, we're going to
put a 0 there as well.

74
00:02:34,290 --> 00:02:35,670
It's sort of like accounting.

75
00:02:35,670 --> 00:02:37,680
If you love accounting
with debits and credits,

76
00:02:37,680 --> 00:02:40,320
trying to get them to equalize,
that's all we're doing here,

77
00:02:40,320 --> 00:02:43,290
is we're trying to whittle
this number down to 0.

78
00:02:43,290 --> 00:02:50,700
So this number right here
10000010 is 130 in decimal.

79
00:02:50,700 --> 00:02:52,590
So let's do one more together.

80
00:02:52,590 --> 00:02:54,630
And let's go ahead and do 16.

81
00:02:54,630 --> 00:02:58,680
The game is, we want to
convert 16 into binary.

82
00:02:58,680 --> 00:03:00,796
We're going to play
the, does it fit game.

83
00:03:00,796 --> 00:03:02,670
So we're going to write
out on our paper 16--

84
00:03:02,670 --> 00:03:03,750
the number we're after--

85
00:03:03,750 --> 00:03:06,420
and ask ourselves the
question, does 128 go in?

86
00:03:06,420 --> 00:03:07,460
The answer is, no--

87
00:03:07,460 --> 00:03:08,310
negative.

88
00:03:08,310 --> 00:03:10,140
Does 64 go into 16?

89
00:03:10,140 --> 00:03:11,640
No-- negative.

90
00:03:11,640 --> 00:03:13,740
Does 32 go into 16?

91
00:03:13,740 --> 00:03:14,430
It does not.

92
00:03:14,430 --> 00:03:16,790
Does 16 going to 16?

93
00:03:16,790 --> 00:03:17,880
[MAKES SIREN NOISE]

94
00:03:17,880 --> 00:03:18,780
The lights go off.

95
00:03:18,780 --> 00:03:20,100
Yes, it does fit.

96
00:03:20,100 --> 00:03:21,600
So we take that
number that we just

97
00:03:21,600 --> 00:03:24,240
put in, we subtract
that from our number,

98
00:03:24,240 --> 00:03:26,910
we take the remainder, and
we play the rest of the game.

99
00:03:26,910 --> 00:03:30,300
You can stop playing until
you've given all 8 bits

100
00:03:30,300 --> 00:03:32,010
in that octet or that byte.

101
00:03:32,010 --> 00:03:35,670
So 8 doesn't go in to 0, nor
does 4, nor does 2, nor does 1.

102
00:03:35,670 --> 00:03:39,750
This is our binary number
that represents 16.

103
00:03:39,750 --> 00:03:43,410
It is 00010000.

104
00:03:43,410 --> 00:03:45,990
So we're going to input--
when we configure routers

105
00:03:45,990 --> 00:03:48,120
and devices with
IP addresses, we're

106
00:03:48,120 --> 00:03:50,070
actually going to put
in the value of 16

107
00:03:50,070 --> 00:03:51,720
for that second octet.

108
00:03:51,720 --> 00:03:53,850
But what the computer
knows, or the router knows,

109
00:03:53,850 --> 00:03:57,930
is that this is the binary
value of that second octet.

110
00:03:57,930 --> 00:04:01,920
I'd like you to take this
number, 33, and your mission--

111
00:04:01,920 --> 00:04:03,510
which I hope you accept--

112
00:04:03,510 --> 00:04:08,940
is to convert 33 into
the 8-bit binary number

113
00:04:08,940 --> 00:04:10,662
that 33 is representing.

114
00:04:10,662 --> 00:04:12,120
What I would
encourage you to do is

115
00:04:12,120 --> 00:04:16,680
start by writing out this table,
and then simply writing out 33

116
00:04:16,680 --> 00:04:19,420
and playing the game
called, does it fit.

117
00:04:19,420 --> 00:04:20,850
So does 128 go in?

118
00:04:20,850 --> 00:04:21,709
Does 64 go in?

119
00:04:21,709 --> 00:04:23,020
Et cetera, et cetera.

120
00:04:23,020 --> 00:04:25,110
Every time it does
go in you put a 1,

121
00:04:25,110 --> 00:04:28,230
and you subtract that
value from your number

122
00:04:28,230 --> 00:04:30,870
and play the game
again, continuing on

123
00:04:30,870 --> 00:04:32,320
with the remainder.

124
00:04:32,320 --> 00:04:36,060
So go ahead pause me right now,
work out the binary equivalent

125
00:04:36,060 --> 00:04:39,040
of the decimal 33, and
when you come back,

126
00:04:39,040 --> 00:04:41,950
we'll validate what that
answer is in binary.

127
00:04:41,950 --> 00:04:44,812
[MUSIC PLAYING]

128
00:04:44,812 --> 00:04:46,094

129
00:04:46,094 --> 00:04:47,260
So the game goes like this--

130
00:04:47,260 --> 00:04:48,940
33 is right here.

131
00:04:48,940 --> 00:04:50,920
We say, does 128 go into 33?

132
00:04:50,920 --> 00:04:51,770
The answer is no.

133
00:04:51,770 --> 00:04:53,080
64 doesn't go in.

134
00:04:53,080 --> 00:04:54,057
32 does.

135
00:04:54,057 --> 00:04:55,390
So we're going to put a 1 there.

136
00:04:55,390 --> 00:04:59,380
We'll say, minus 32,
and our remainder is 1.

137
00:04:59,380 --> 00:05:00,460
16 doesn't go.

138
00:05:00,460 --> 00:05:01,210
Nor does 8.

139
00:05:01,210 --> 00:05:01,900
Nor does 4.

140
00:05:01,900 --> 00:05:02,410
Nor does 2.

141
00:05:02,410 --> 00:05:04,630
But 1 goes in cleanly one time.

142
00:05:04,630 --> 00:05:07,720
And our accountant is
happy because we've

143
00:05:07,720 --> 00:05:11,000
had a zero balance at the end,
which is how it should be.

144
00:05:11,000 --> 00:05:15,100
So the decimal number of 33 is
representing our binary number

145
00:05:15,100 --> 00:05:19,060
of 00100001.

146
00:05:19,060 --> 00:05:23,470
If that's the answer that you've
got, absolutely, great job.

147
00:05:23,470 --> 00:05:25,690
I hope this has been
informative for you.

148
00:05:25,690 --> 00:05:28,012
And I'd like to thank
you for viewing.

149
00:05:28,012 --> 00:05:28,512