1
00:00:05,500 --> 00:00:09,600
In this video, we'll go over c++ arithmetic operators.

2
00:00:10,000 --> 00:00:13,800
These are exactly the ones you expect. The + symbol means addition. 

3
00:00:14,160 --> 00:00:18,460
the - symbol mean subtraction, the * is multiplication,

4
00:00:18,460 --> 00:00:20,260
the / is division, 

5
00:00:20,260 --> 00:00:24,560
and the % symbol is the modulo operator or the remainder of division.

6
00:00:25,060 --> 00:00:28,660
You may not be familiar with this operator, but that's okay, we'll cover it toward the end of the video.

7
00:00:29,320 --> 00:00:33,320
The +,  -, *,  and / operators are overloaded.

8
00:00:33,320 --> 00:00:35,920
What that means is that work with different types.

9
00:00:35,920 --> 00:00:39,720
So we can add two integers, we can add two floats, we can add two doubles

10
00:00:39,720 --> 00:00:41,520
by simply using the plus symbol.

11
00:00:41,850 --> 00:00:44,850
The same is true for, subtraction, multiplication, division.

12
00:00:45,250 --> 00:00:47,910
The modulo operator only works with integers.

13
00:00:47,910 --> 00:00:49,910
And again, I'll show you an example of that in a little bit.

14
00:00:50,310 --> 00:00:52,310
So let's try a few examples here.

15
00:00:52,810 --> 00:00:55,210
In the code done here, you can see that I've declared

16
00:00:55,210 --> 00:00:57,710
two integers: num1 and num2

17
00:00:57,710 --> 00:01:00,610
and I've assigned 200 and 100 to them, respectively.

18
00:01:00,610 --> 00:01:04,489
Again, these are integers. You could do this with doubles or floats or anything you'd like

19
00:01:04,489 --> 00:01:05,890
but I'm just going to use integers here.

20
00:01:06,390 --> 00:01:10,690
You can see that this first line,  this first output statement, right here.

21
00:01:11,050 --> 00:01:14,410
Let's walk through that really quickly so we're clear as to what's going on here.

22
00:01:14,910 --> 00:01:17,410
Remember, we've got expressions here.

23
00:01:17,410 --> 00:01:20,010
So num1 is an expression, num2 is an expression

24
00:01:20,010 --> 00:01:22,310
and that addition expression

25
00:01:22,810 --> 00:01:25,810
is evaluated to the sum of num1 and num2.

26
00:01:25,810 --> 00:01:29,810
So in this this case, num1 is 200 so this will be replaced with 200.

27
00:01:31,310 --> 00:01:35,110
Num2 is 100, and this will be replaced with 100.

28
00:01:35,610 --> 00:01:39,610
And then num1 + num2 will be added together, that's why the plus is there

29
00:01:39,610 --> 00:01:41,110
and this will give us 300.

30
00:01:41,910 --> 00:01:44,510
Okay. Now these guys are inside

31
00:01:44,510 --> 00:01:47,630
quotes so there are string literals and that would be printed out as is.

32
00:01:48,130 --> 00:01:52,430
So what we expect here is 200 + 100 equals 300 and of course, we've got

33
00:01:52,790 --> 00:01:55,090
the new line or the end line at the end.

34
00:01:55,690 --> 00:01:57,190
All right. So let's run this

35
00:01:57,990 --> 00:02:00,290
and see if we get what we expect.

36
00:02:01,190 --> 00:02:05,290
And exactly that's what happens. 200 plus 100 equals 300.

37
00:02:05,290 --> 00:02:09,490
Okay. So let me comment that line out and

38
00:02:10,090 --> 00:02:13,990
what we could do is rather than do that calculation

39
00:02:13,990 --> 00:02:15,290
right in line right here,

40
00:02:15,790 --> 00:02:19,290
we could simply do the calculation and assign it to a variable.

41
00:02:19,490 --> 00:02:22,790
In this case, let's create a variable called result.

42
00:02:25,090 --> 00:02:28,390
And we'll initialize it to 0. And all were saying is

43
00:02:28,640 --> 00:02:32,840
add num1 and num2 that'll give us 300 and assign that result

44
00:02:33,040 --> 00:02:36,400
to the result variable. Okay. So we're going to add

45
00:02:36,600 --> 00:02:41,100
200 + 100, that gives us 300, and we're storing 300 into result.

46
00:02:41,500 --> 00:02:46,100
And then rather than do the calculation here, as we did, we're just going to print out result.

47
00:02:46,500 --> 00:02:49,940
It's as easy as that. So when I run this now, I should have the same

48
00:02:49,940 --> 00:02:51,140
exact output,

49
00:02:51,140 --> 00:02:53,140
200 plus 100 equals 300.

50
00:02:54,140 --> 00:02:58,440
So now let me comment out some of these, and we'll walk through these real quick.

51
00:02:59,140 --> 00:03:00,440
And I'll do it right up to there.

52
00:03:01,540 --> 00:03:04,040
So this next one here on line 29,

53
00:03:04,040 --> 00:03:06,540
I'm simply subtracting num1

54
00:03:06,540 --> 00:03:09,340
- num2, storing the difference in result

55
00:03:09,340 --> 00:03:10,940
and then I'm out putting result.

56
00:03:10,940 --> 00:03:14,540
So here, we would expect 200 - 100, we'd expect 100.

57
00:03:15,140 --> 00:03:17,740
On line 32, we're multiplying the 2.

58
00:03:18,040 --> 00:03:20,340
This is different from algebra.

59
00:03:20,340 --> 00:03:23,700
Do you have to have that multiplication symbol, that asterisk.

60
00:03:23,700 --> 00:03:28,000
You can't just say num1, num2 or something like that like you were doing algebra,

61
00:03:28,000 --> 00:03:30,360
you just put the two things together. You can't use

62
00:03:30,360 --> 00:03:33,360
a dot like you could  in algebras as well. It's got to be

63
00:03:33,860 --> 00:03:36,660
the multiplication operator, which is the asterisk.

64
00:03:36,660 --> 00:03:40,960
So we're going to multiply num1 and num2 that will give us 20,000, which we store in result,

65
00:03:41,260 --> 00:03:42,620
and we're displaying that.

66
00:03:42,620 --> 00:03:48,210
And then the third one would be result is num1 divided by num2,

67
00:03:48,210 --> 00:03:49,910
that's on line 35.

68
00:03:49,910 --> 00:03:53,570
And we're going to store that quotient into result.

69
00:03:54,870 --> 00:03:57,570
There we would expect 200/100, it gives us 2.

70
00:03:57,570 --> 00:04:00,670
Okay. So let's run what we've got right here and

71
00:04:01,270 --> 00:04:02,630
see what our results are.

72
00:04:02,630 --> 00:04:05,930
So we've got 200 + 100, like we did before is 300.

73
00:04:06,230 --> 00:04:10,430
200 - 100 is a 100. 200 * 100 is 20000.

74
00:04:10,630 --> 00:04:12,630
And 200/100 is 2.

75
00:04:13,030 --> 00:04:16,930
Okay. So this is exactly like you would expect. It's really, really simple.

76
00:04:16,930 --> 00:04:19,290
Math works just like you expected to.

77
00:04:19,790 --> 00:04:23,490
Now something you may not expect is this result right here on line 38.

78
00:04:23,490 --> 00:04:24,990
I'm going to uncomment this.

79
00:04:26,690 --> 00:04:28,690
And in this case, what I'm doing is

80
00:04:28,690 --> 00:04:31,190
I'm dividing num2/num1.

81
00:04:31,690 --> 00:04:34,890
Okay. Remember, num2 is 100 and num1 is 200.

82
00:04:34,890 --> 00:04:38,690
So what's happening here is I'm dividing 100

83
00:04:38,690 --> 00:04:42,460
/200. You would expect 0.5.

84
00:04:42,460 --> 00:04:45,660
That's not what you get. We're doing integer division.

85
00:04:45,660 --> 00:04:49,260
Okay. So there are no digits after the decimal point.

86
00:04:49,260 --> 00:04:52,620
We're working with whole numbers only. So in this case,

87
00:04:52,620 --> 00:04:54,920
what happens is 100

88
00:04:55,720 --> 00:04:57,720
gets divided by 200.

89
00:04:59,120 --> 00:05:02,820
And the results if this if these were doubles would be 0.5.

90
00:05:03,220 --> 00:05:06,420
But we're working with integers. So this piece is just chopped right off

91
00:05:06,420 --> 00:05:07,720
so we end up with a 0.

92
00:05:08,120 --> 00:05:09,920
Okay. So let's run this.

93
00:05:13,120 --> 00:05:16,320
And you can see here 100/200 is 0.

94
00:05:16,320 --> 00:05:20,320
You've got to be really careful when you're doing division with whole numbers or integers

95
00:05:20,320 --> 00:05:21,980
because this is the behavior.

96
00:05:21,980 --> 00:05:25,230
If you need to 0.5, you want to be really, really precise,

97
00:05:25,230 --> 00:05:27,730
then you need to use doubles, not integers.

98
00:05:27,730 --> 00:05:29,930
And I'll show you an example using doubles in a second.

99
00:05:30,920 --> 00:05:34,920
Now let's look at the modular operator or the remainder of operator.

100
00:05:34,920 --> 00:05:37,920
In this case, right here,

101
00:05:38,420 --> 00:05:41,020
I'm saying num1 mod num2.

102
00:05:41,620 --> 00:05:44,390
Again, what's num1, it’s 200.

103
00:05:44,390 --> 00:05:46,190
What's num2, 100.

104
00:05:46,190 --> 00:05:50,190
So 200 divided by, let me write that out real clear

105
00:05:50,190 --> 00:05:53,490
so it's not confusing it all. So we're going to say 200

106
00:05:55,790 --> 00:05:58,150
divided by 100.

107
00:05:58,950 --> 00:06:02,940
The result of this is 2 with a remainder of 0.

108
00:06:03,340 --> 00:06:05,640
That's the modular operator.

109
00:06:05,640 --> 00:06:09,740
It's only interested in the remainder. So in this case, it’ll print out a 0.

110
00:06:10,240 --> 00:06:14,240
The next line, I’ll uncomment that out in a second. But the next line we're going to say

111
00:06:14,440 --> 00:06:17,240
right here, num1

112
00:06:17,940 --> 00:06:20,540
let me clear that draw that line a little nicer there.

113
00:06:20,540 --> 00:06:24,340
Here we're saying num1 mod num2. So we're saying 10

114
00:06:24,740 --> 00:06:25,740
mod 3.

115
00:06:25,740 --> 00:06:28,100
Remember, this only works with integers.

116
00:06:28,100 --> 00:06:30,400
So the results of the division would

117
00:06:30,400 --> 00:06:32,600
be 3 with a remainder of 1,

118
00:06:32,600 --> 00:06:35,500
number 3 x 3 is 9 and you get the 1 remainder.

119
00:06:35,500 --> 00:06:39,300
That's the result of the modular operator. It's a pretty handy operator.

120
00:06:39,700 --> 00:06:43,400
So let me clear this and I'll uncomment these few lines of code right here.

121
00:06:45,000 --> 00:06:46,000
And we will run this.

122
00:06:49,800 --> 00:06:51,600
And let's take a look at the result.

123
00:06:51,600 --> 00:06:54,100
So here we go. 200 mod 100

124
00:06:54,100 --> 00:06:58,200
is 0, right that's the remainder because we get a 2 with a remainder of 0.

125
00:06:58,500 --> 00:07:00,700
And then this case 10 mod 3

126
00:07:00,700 --> 00:07:05,200
is 1 because we get a 3 with a remainder of 1 when we divided by 3.

127
00:07:05,500 --> 00:07:08,200
This could be a really, really handy operator to use.

128
00:07:08,200 --> 00:07:12,300
And in the challenge exercise, you're going to have to use it to solve the problem.

129
00:07:12,900 --> 00:07:16,000
A couple more things. Just like you can with

130
00:07:16,000 --> 00:07:18,800
any programming language and doing any kind of math, we can add and

131
00:07:18,800 --> 00:07:22,100
divide and subtract and we can do everything in line.

132
00:07:22,700 --> 00:07:24,300
It's important to understand

133
00:07:24,300 --> 00:07:27,500
that the precedents or the order in which this stuff

134
00:07:27,500 --> 00:07:30,600
happens is the same precedents you probably learned in grade school.

135
00:07:31,100 --> 00:07:33,400
Here in the US, we learned PEMDAS.

136
00:07:35,100 --> 00:07:37,800
That was the acronym we used which meant parentheses

137
00:07:37,800 --> 00:07:41,000
first then exponents then multiplication and division

138
00:07:41,000 --> 00:07:42,900
and then addition and subtraction.

139
00:07:42,900 --> 00:07:47,260
You may have learned something else if you're from a different country, but that's what we learned here.

140
00:07:47,260 --> 00:07:49,060
So what this means is that

141
00:07:49,060 --> 00:07:52,960
multiplication and division happened before addition and subtraction, right.

142
00:07:52,960 --> 00:07:55,460
So in this case what’s going to happen is num1

143
00:07:55,760 --> 00:07:58,860
is going to be multiplied by 10 and then

144
00:07:58,860 --> 00:08:00,860
we're going to add num2 to that result,

145
00:08:01,660 --> 00:08:04,260
right. If you want something else,

146
00:08:04,260 --> 00:08:07,260
if you want to add the 10 in the num2 first,

147
00:08:07,260 --> 00:08:10,860
then you need to use parentheses around there like that.

148
00:08:11,760 --> 00:08:15,660
It's as simple as that and again it's something that we're all used to by now.

149
00:08:16,260 --> 00:08:20,960
Let me clear this and then I'll do this last example with the division.

150
00:08:22,560 --> 00:08:24,160
I'll comment these two lines out.

151
00:08:26,360 --> 00:08:30,460
So in this case, I'm outputting 5/10.

152
00:08:31,060 --> 00:08:33,360
Remember, this is using integer division.

153
00:08:33,360 --> 00:08:37,020
So 5/10 is 0, not 0.5.

154
00:08:37,919 --> 00:08:38,820
In this case,

155
00:08:38,820 --> 00:08:42,820
5.0/10.0 is 0.5

156
00:08:42,820 --> 00:08:44,420
because we're using doubles here.

157
00:08:45,220 --> 00:08:47,820
In a couple of videos from now, we're going to do a video

158
00:08:47,820 --> 00:08:51,720
where we're mixing types, we will be multiplying and dividing integers and doubles all together

159
00:08:51,720 --> 00:08:54,820
on the same expression. In that case,

160
00:08:54,820 --> 00:08:58,620
we can use casts to tell the compiler,hey, you know what,

161
00:08:58,620 --> 00:09:02,920
I really want this to be a double instead of an integer, even though it looks like an integer there.

162
00:09:03,220 --> 00:09:07,320
And so we'll get to that in a minute. And let me run this thing one more time.

163
00:09:08,920 --> 00:09:10,720
And you can see the last two

164
00:09:11,520 --> 00:09:14,820
results right down here 5/10 is 0

165
00:09:14,820 --> 00:09:18,420
and 5.0/10.0 is 0.5.

166
00:09:20,120 --> 00:09:24,220
Okay. So now let's solve a real problem. Let's convert

167
00:09:24,220 --> 00:09:25,920
Euros to U.S. dollars

168
00:09:26,280 --> 00:09:28,480
and I've created a

169
00:09:28,880 --> 00:09:31,180
project in the section 8 workspace,

170
00:09:31,180 --> 00:09:32,080
called Euros.

171
00:09:32,080 --> 00:09:35,580
This project that I worked on right here is called arithmetic operator

172
00:09:35,580 --> 00:09:37,180
so you can refer to that if you like.

173
00:09:37,180 --> 00:09:40,880
But I've created a project called Euros and that's when we'll get to next.

174
00:09:41,680 --> 00:09:46,280
Okay. So I've opened up the main CPP file in the Euros project.

175
00:09:46,780 --> 00:09:48,780
Right now there's really not much in here.

176
00:09:48,780 --> 00:09:52,480
I'm just printing a new line at the end to separate that little time message

177
00:09:52,480 --> 00:09:54,080
that is displayed at the end

178
00:09:54,330 --> 00:09:57,630
and there's no real code here. We're going to write the code from scratch.

179
00:09:57,630 --> 00:09:59,530
So what we want to do is we want to convert

180
00:09:59,530 --> 00:10:03,430
Euros to US dollar. So obviously we need some sort of conversion factor.

181
00:10:03,830 --> 00:10:06,430
I just went on Google now and I saw that

182
00:10:06,430 --> 00:10:08,730
you have 1.19

183
00:10:09,090 --> 00:10:14,080
dollars per Euro. Okay. So 1 euro is 1.19 dollar.

184
00:10:14,280 --> 00:10:16,940
So we need to use that value somewhere.

185
00:10:16,940 --> 00:10:20,240
Now that's going to be a constant. So let's just find that as a constant.

186
00:10:20,240 --> 00:10:22,840
We can do it right here. We could say const.

187
00:10:22,840 --> 00:10:26,640
We want it to be a double right because it's not an integer, it’s 1.19

188
00:10:26,640 --> 00:10:30,840
and we'll give it a name. We will call it US dollars per Euro,

189
00:10:33,040 --> 00:10:34,040
per EUR.

190
00:10:34,540 --> 00:10:37,640
And we will initialized that to 1.19.

191
00:10:38,640 --> 00:10:40,440
And don't forget the semicolon.

192
00:10:40,440 --> 00:10:43,340
So now we've declared that constant US dollars

193
00:10:43,340 --> 00:10:45,540
per Euro to be 1.19.

194
00:10:45,540 --> 00:10:47,840
It's not going to change even accidentally.

195
00:10:49,140 --> 00:10:50,440
Now what do we need to do?

196
00:10:50,440 --> 00:10:53,940
Well, we need to output a message to the user. We will say cout.

197
00:10:54,540 --> 00:10:58,640
We will say welcome to the EUR

198
00:10:59,440 --> 00:11:01,440
to USD converter

199
00:11:02,140 --> 00:11:03,440
or something like that.

200
00:11:05,640 --> 00:11:07,640
And we'll put an endline at the end.

201
00:11:08,640 --> 00:11:10,940
We need to ask the user to enter

202
00:11:10,940 --> 00:11:14,240
the value in Euros, right and that's the whole idea. So cout,

203
00:11:14,440 --> 00:11:17,840
we will say enter the value

204
00:11:20,840 --> 00:11:22,040
in Euros,

205
00:11:24,040 --> 00:11:25,640
and we'll do something like that.

206
00:11:26,190 --> 00:11:29,690
We won't put a new line there because we want the user to

207
00:11:29,690 --> 00:11:31,190
type something and right next to it.

208
00:11:31,990 --> 00:11:35,990
What do we do next? Well, we need to do a few things. We need – remember,

209
00:11:35,990 --> 00:11:39,980
most of these programs are input, processing and then output.

210
00:11:40,180 --> 00:11:43,180
We need input. We need to read in from cin,

211
00:11:43,480 --> 00:11:47,280
the number of Euros that they want to convert, right? So we need to have something like

212
00:11:47,680 --> 00:11:49,680
cin into

213
00:11:50,480 --> 00:11:51,380
euros.

214
00:11:52,480 --> 00:11:55,280
So we need to define that variable right here.

215
00:11:56,080 --> 00:11:59,380
So let's do that right in here. We'll say double.

216
00:12:00,980 --> 00:12:02,680
We will call it Euros. That's a good name,

217
00:12:03,680 --> 00:12:05,880
and will initialize it to 0.0.

218
00:12:05,880 --> 00:12:08,880
That way we know we've got a 0 value in there.

219
00:12:10,240 --> 00:12:12,910
We know we're going to convert this to dollars, right. So we may as well

220
00:12:12,910 --> 00:12:16,210
create our dollars variable as well. So we can say double,

221
00:12:18,410 --> 00:12:19,910
and we can call it dollars.

222
00:12:21,010 --> 00:12:23,210
And again 0.0.

223
00:12:25,710 --> 00:12:29,910
Perfect. Now we're right in the Euros. We need to convert

224
00:12:30,270 --> 00:12:34,470
the Euros to Dollars. How do we do that? We just use a real simple multiplication.

225
00:12:34,470 --> 00:12:37,970
We can say that the number of Dollars is equal to

226
00:12:38,470 --> 00:12:40,070
again the number of euros

227
00:12:41,070 --> 00:12:44,070
x the const that we have,

228
00:12:45,170 --> 00:12:46,170
dollars per Euro.

229
00:12:47,470 --> 00:12:51,670
And now all we need is that final output statement. Let me scroll up just a little bit

230
00:12:51,670 --> 00:12:53,870
and we will say something like cout

231
00:12:54,370 --> 00:12:57,970
and we'll say the Euros, whatever they entered

232
00:13:00,570 --> 00:13:03,870
is equivalent to or we will actually say Euros,

233
00:13:03,870 --> 00:13:06,370
that'll be nice so that I can read it better is

234
00:13:07,470 --> 00:13:09,170
equivalent to,

235
00:13:10,870 --> 00:13:13,070
you put another insertion operator here,

236
00:13:13,870 --> 00:13:17,170
we will type in dollars, whatever the conversion was

237
00:13:17,420 --> 00:13:20,420
and then we will just type string dollar, so it's nice and readable.

238
00:13:21,520 --> 00:13:24,520
That's it. We will put a new line at the end line

239
00:13:25,220 --> 00:13:27,020
and that should be it.

240
00:13:27,620 --> 00:13:30,020
Let's run this and see if we have any errors.

241
00:13:30,020 --> 00:13:32,720
We will test it to make sure we don't have any errors

242
00:13:32,720 --> 00:13:34,720
and we will debug it if we do have any errors.

243
00:13:34,720 --> 00:13:38,380
All right. So I'm going to save, and I'm going to press ctrl F5 to run.

244
00:13:39,180 --> 00:13:41,180
There is no compiler error so that's great.

245
00:13:41,380 --> 00:13:44,980
So enter the value in Euros. Well, let's type in 1 euro, right.

246
00:13:44,980 --> 00:13:48,750
If we type in 1 euro, we expect back 1.19 dollar.

247
00:13:48,750 --> 00:13:52,350
That would be a real simple and good test case. 1,

248
00:13:53,150 --> 00:13:56,950
we get 1 euro is equivalent to 1.19 dollars.

249
00:13:57,250 --> 00:13:59,450
Good. Let's try another one.

250
00:14:02,050 --> 00:14:02,950
Let’s run.

251
00:14:04,250 --> 00:14:09,150
How about 123.5 Euros.

252
00:14:09,950 --> 00:14:13,950
We get back 146.965 dollars. Don't worry about the

253
00:14:13,950 --> 00:14:16,950
precision and the dollars and cents. We will learn how to

254
00:14:16,950 --> 00:14:19,750
format output a little bit later. That's it.

255
00:14:19,750 --> 00:14:23,450
That's the program. Really, really simple. You can see what we're doing here is we're

256
00:14:23,450 --> 00:14:27,810
using the things that we've learned, right? We're using our cin. We're using our cout.

257
00:14:27,810 --> 00:14:30,410
We've got a constant to find right here.

258
00:14:30,410 --> 00:14:34,070
We've got some variables that we need here and we’re initializing them to 0.

259
00:14:34,670 --> 00:14:38,660
And we're doing our calculation here using one of the arithmetic operators,

260
00:14:38,660 --> 00:14:39,960
the multiplication symbol.

261
00:14:40,760 --> 00:14:45,020
I encourage you to write one of these programs on your own.

262
00:14:45,020 --> 00:14:48,620
Write, I don't know, something to something converter, Fahrenheit to Celsius,

263
00:14:48,620 --> 00:14:52,620
kilometers to miles, yards to inches, meters to centimeters.

264
00:14:52,620 --> 00:14:55,620
Write one of these programs just like that, that'll give you a good practice.