1 00:00:01,190 --> 00:00:10,070 OK, so we are now at the point in which we are going to go over and not only just putting data into 2 00:00:10,070 --> 00:00:16,220 our own programs, but getting data from the user to use in our programs. 3 00:00:17,030 --> 00:00:21,800 So up until this point, we have kind of been making these standalone programs that are almost just 4 00:00:21,800 --> 00:00:25,520 like a simulation rather than an interactive program, right? 5 00:00:26,210 --> 00:00:33,530 We've just been hard coding, like making our own data into the program, into the file that we write 6 00:00:33,530 --> 00:00:35,630 the code in and then we run it. 7 00:00:35,630 --> 00:00:38,450 And it just kind of does something and shows us something. 8 00:00:38,450 --> 00:00:40,900 But that's kind of a simulation. 9 00:00:40,910 --> 00:00:42,920 It doesn't allow us to interact with it. 10 00:00:43,490 --> 00:00:49,130 Modern software you notice on your computer like you can normally click things and whatever software 11 00:00:49,130 --> 00:00:53,880 you are using or you can type things, and we're going to get into that realm right now. 12 00:00:53,900 --> 00:00:58,250 Of course, we're going to start out with the easier thing, which is typing things and specifically 13 00:00:58,250 --> 00:01:01,280 typing things into the console. 14 00:01:01,520 --> 00:01:02,750 What do I mean by console? 15 00:01:02,750 --> 00:01:07,850 If you forgot what that was, it is similar to kind of what is in the terminal. 16 00:01:08,120 --> 00:01:09,080 We use the terminal. 17 00:01:09,080 --> 00:01:15,470 The terminal can kind of double as a console because when we run the program, we notice that our output 18 00:01:15,470 --> 00:01:19,400 like Hello World and stuff was going to be terminal there. 19 00:01:19,520 --> 00:01:20,990 So it's kind of seen as the console. 20 00:01:21,350 --> 00:01:25,880 Also, the console could be at the bottom of the screen or something in your I.D. or. 21 00:01:26,940 --> 00:01:31,710 You know, wherever it's just kind of a box where the output goes and it shows you the output, so wherever 22 00:01:31,710 --> 00:01:37,530 your hello world and other text that we've been using or mathematical operations that were printed using 23 00:01:37,530 --> 00:01:41,350 the sea out, wherever that showed up, that's kind of what the council is. 24 00:01:41,480 --> 00:01:42,750 I just wanted to point that out. 25 00:01:44,310 --> 00:01:47,700 So specifically today, we're going to be talking about the sea in object. 26 00:01:49,570 --> 00:01:51,100 So what is the see in object? 27 00:01:51,820 --> 00:01:59,260 Well, we've already seen the sea out object for output streams, so it's seen is very similar, but 28 00:01:59,260 --> 00:02:01,750 instead of an output stream, it's an input stream. 29 00:02:02,470 --> 00:02:08,530 So when we use sea in a C++ code, what it does is enable us to capture keyboard input. 30 00:02:08,530 --> 00:02:15,730 So the keystrokes that the user is typing after they run the program in the console, which the user 31 00:02:15,730 --> 00:02:19,270 in this case will be us because we'll be testing our own programs. 32 00:02:21,710 --> 00:02:25,400 So the keyboard input is saved to something called the keyboard buffer. 33 00:02:25,700 --> 00:02:32,240 So just imagine this buffer as a magic array where it just contains all this stuff that's been entered 34 00:02:32,240 --> 00:02:34,100 and it all happens behind the scenes. 35 00:02:34,130 --> 00:02:39,590 So I'm not going to get into too much granular detail about it because I think that it's kind of defeating 36 00:02:39,590 --> 00:02:43,040 the point of the reason that I'm introducing this right now. 37 00:02:44,780 --> 00:02:50,930 So rather than just using the stream insertion operator as we have with see out, that was the less 38 00:02:50,930 --> 00:02:54,380 than less than sign that came after the word sea out. 39 00:02:55,280 --> 00:02:56,990 We're going to flip that around. 40 00:02:56,990 --> 00:03:02,450 So it's going to look like this right here, and this is something called the stream extraction operator 41 00:03:02,450 --> 00:03:05,480 instead of insertion operators, the extraction operator. 42 00:03:06,200 --> 00:03:08,270 So when you use it, it looks something like this. 43 00:03:08,270 --> 00:03:10,460 We put the word see in rather than see out. 44 00:03:10,460 --> 00:03:16,340 And then we put these this flipped symbol here greater than greater than and then we read it into a 45 00:03:16,340 --> 00:03:16,910 variable. 46 00:03:19,850 --> 00:03:26,450 So here's a really basic example I make an integer variable that I declare, then I use scene to read 47 00:03:26,750 --> 00:03:29,650 the console input into this integer. 48 00:03:29,660 --> 00:03:35,750 So what's happening here is something that's kind of the exact opposite of what we did with see. 49 00:03:35,960 --> 00:03:43,130 So see out had is basically instead of seeing we had a out, then we had these flipped right, so the 50 00:03:43,130 --> 00:03:45,620 openings were facing to the right. 51 00:03:46,730 --> 00:03:52,310 Agree there was like the they were less than science, so the greater than part, the opening is we're 52 00:03:52,310 --> 00:03:54,050 facing this way toward the variable. 53 00:03:54,740 --> 00:04:00,260 And remember how I'd kind of described in a previous lecture that it's like our data from the variable 54 00:04:00,650 --> 00:04:07,610 was flowing through those openings into the console out, which is see out, sort it flowing out to 55 00:04:07,610 --> 00:04:10,180 the console for that console out. 56 00:04:10,190 --> 00:04:11,450 This is console in. 57 00:04:11,930 --> 00:04:13,970 So the data is coming from the other direction. 58 00:04:13,970 --> 00:04:20,270 The data is flowing from the console through these openings into the variable. 59 00:04:21,720 --> 00:04:22,890 So that's the difference now. 60 00:04:23,970 --> 00:04:28,380 So what happens is when you run the program in the console or terminal, wherever you want to think 61 00:04:28,380 --> 00:04:32,390 of that S and the C in line and your code is reached. 62 00:04:32,400 --> 00:04:38,580 So this is like at this point, it's machine code, but once the computer recognizes that scene line 63 00:04:38,580 --> 00:04:39,360 that you coded. 64 00:04:40,320 --> 00:04:45,510 The program is going to stall at that point, so it'll pause and say, OK, I'm going to wait for the 65 00:04:45,510 --> 00:04:52,650 user to type something now, so it'll stall, wait for the user to type something and really important 66 00:04:52,650 --> 00:04:53,350 point here. 67 00:04:53,910 --> 00:04:57,900 So it does not continue until you press enter. 68 00:04:59,500 --> 00:05:07,360 And it won't always automatically continue when you press enter, it kind of depends on what your program 69 00:05:07,360 --> 00:05:11,110 is expecting, like how much input your program is expecting. 70 00:05:11,110 --> 00:05:19,420 But if you type enough stuff to satisfy the requirement of input from the program and you press enter, 71 00:05:20,290 --> 00:05:24,640 then the program will have a chance to continue executing. 72 00:05:25,850 --> 00:05:32,420 If you have more seen stuff, then it might ask you to, it might prompt you stall again and have you 73 00:05:32,420 --> 00:05:39,440 enter more until you keep pressing enter and you have kind of fulfilled all that CNN requirement, then 74 00:05:39,440 --> 00:05:40,940 it will be able to finish the program. 75 00:05:42,490 --> 00:05:49,000 So seeing at that point will automatically attempt to convert whatever you typed as input into, in 76 00:05:49,000 --> 00:05:50,290 this case, an integer. 77 00:05:50,500 --> 00:05:54,190 But really, it has to do with whatever type the variable is. 78 00:05:54,520 --> 00:05:59,710 If this was a float, seeing would attempt to convert the input you typed into a float. 79 00:05:59,920 --> 00:06:02,560 Same thing with char, it would try and turn it into a char. 80 00:06:03,880 --> 00:06:10,630 Then what happens, of course, is that data gets stored into the mine and variable and really important 81 00:06:10,630 --> 00:06:18,040 thing about the typing, though the the type of the variable is what I mean, because if you enter something, 82 00:06:18,610 --> 00:06:21,370 if you press some keyboard keys and keystrokes. 83 00:06:22,460 --> 00:06:29,090 That are not the same, really, as the data type that was expected for the variable that can lead to 84 00:06:29,090 --> 00:06:32,710 some strange, strange behavior and stuff. 85 00:06:32,720 --> 00:06:35,900 So we'll see that later on in this lecture. 86 00:06:36,680 --> 00:06:38,180 So that's an important detail. 87 00:06:39,620 --> 00:06:44,090 So let's look at a full example, so slightly more comprehensive, it's an actual program. 88 00:06:44,990 --> 00:06:46,380 Let's go ahead and trace through this. 89 00:06:46,400 --> 00:06:51,920 It's a program that just calculates the area of a rectangle that the user provides the width and height 90 00:06:51,920 --> 00:06:52,220 for. 91 00:06:53,000 --> 00:06:55,190 So I'm going to go over every single line. 92 00:06:56,150 --> 00:07:00,680 It may seem redundant, but I'm doing this just because I think that it can't hurt. 93 00:07:01,130 --> 00:07:08,030 And if there might, maybe there's some people out there that are still a little confused on the flow 94 00:07:08,030 --> 00:07:11,210 of some of these introductory programs we've been writing. 95 00:07:11,220 --> 00:07:16,730 And so I would like to just go step by step since I haven't really had a chance to do that a lot. 96 00:07:16,730 --> 00:07:24,860 And hopefully that will help solidify things for the potential people that may not completely grasp 97 00:07:24,860 --> 00:07:27,200 how our current programs are working. 98 00:07:29,110 --> 00:07:35,830 So first line here is the include directive, and specifically it's including EO stream. 99 00:07:36,370 --> 00:07:42,340 This enables us not only to use the C out that we've been using, but also the C in that we are just 100 00:07:42,340 --> 00:07:43,270 learning about now. 101 00:07:43,270 --> 00:07:50,380 So seeing as part of our stream as well in this specific program, we are deciding to use the namespace. 102 00:07:50,410 --> 00:07:51,430 Of course you don't have to. 103 00:07:51,440 --> 00:07:57,220 You could put a Stevie Colon colon in front of the C out and would also need to put Stevie Colon colon 104 00:07:57,490 --> 00:08:01,510 in front of the C, and if you did not choose to use that standard namespace. 105 00:08:03,900 --> 00:08:06,240 Next, we define our main function, of course. 106 00:08:07,200 --> 00:08:12,180 Then we declare a width integer variable. 107 00:08:13,050 --> 00:08:15,150 So this will be used to store the width of the rectangle. 108 00:08:16,020 --> 00:08:16,710 Same thing. 109 00:08:16,980 --> 00:08:19,680 This is going to be used. 110 00:08:20,100 --> 00:08:21,290 It's called height, and it's not. 111 00:08:21,300 --> 00:08:22,110 This is a typo. 112 00:08:22,140 --> 00:08:25,070 It's not supposed to be used to store the width. 113 00:08:25,080 --> 00:08:27,030 It's going to be used to store the height. 114 00:08:28,900 --> 00:08:34,960 And then we print out a little message to the user to ask them to please enter the width. 115 00:08:36,150 --> 00:08:42,290 So this is printing out to the console, and it's going to prompt them to enter a value for it. 116 00:08:43,140 --> 00:08:52,070 Next, we actually read that stuff that they typed into the width variable using in on the next line. 117 00:08:52,080 --> 00:08:53,510 We do the same thing with the hype. 118 00:08:53,520 --> 00:08:58,620 We ask the user by showing a message printing to the console for them to enter the hype. 119 00:09:00,260 --> 00:09:08,330 Then once again, we you see end to read whatever they typed into the height variable now on this last 120 00:09:08,690 --> 00:09:14,750 informative, kind of useful line, we print out the area of the rectangle, so we have a little message 121 00:09:14,750 --> 00:09:17,780 here that says the area of the rectangle is. 122 00:09:17,780 --> 00:09:23,600 And then after that we see out another thing, which is the width times, the height we are using the 123 00:09:23,600 --> 00:09:27,020 multiplication operator, similar to how you've seen in previous lectures. 124 00:09:27,530 --> 00:09:33,620 And we're multiplying these two variables that hold the values that came from the user. 125 00:09:34,710 --> 00:09:38,460 The width from line eight and the height from line 10. 126 00:09:38,790 --> 00:09:45,180 Then we have an in line at the end here, the main function returns a successful exit code back to the 127 00:09:45,180 --> 00:09:47,160 operating system and our program is finished. 128 00:09:49,540 --> 00:09:54,190 So that's a pretty simple example, this consider another example, so the only difference in this one 129 00:09:54,190 --> 00:09:59,640 is that we have three variables and that we are not taking them in on separate lines. 130 00:09:59,650 --> 00:10:02,860 We are taking the input in all on the same line. 131 00:10:02,980 --> 00:10:06,100 And the same line is which we print out the message. 132 00:10:06,730 --> 00:10:11,380 So we print out a message that says enter label width height all at once. 133 00:10:12,530 --> 00:10:14,840 So it kind of prompts the user to enter them all at once. 134 00:10:15,650 --> 00:10:21,470 Then what we do is on that same line, we read it in with CNN, so we read in. 135 00:10:22,320 --> 00:10:28,100 Here's the extraction operator and we noticed that the extraction operators are separating in all three 136 00:10:28,100 --> 00:10:29,120 of our variables here. 137 00:10:29,120 --> 00:10:31,880 So we're reading in the label the width in the height. 138 00:10:31,890 --> 00:10:37,670 So this time our rectangle has not only a width and height, but also a label which is expected as the 139 00:10:37,670 --> 00:10:39,650 first input for the user to enter. 140 00:10:41,310 --> 00:10:42,990 Then we calculate it down here, of course. 141 00:10:44,600 --> 00:10:50,870 So this is us choosing to have the user enter everything on one line in the same line as which we prompted 142 00:10:50,870 --> 00:10:52,010 them with the see out. 143 00:10:53,970 --> 00:10:58,620 So let's take a look at what happens on the other side of things, so not in the text of our program, 144 00:10:58,980 --> 00:11:02,400 but what happens when we run our program and what the user sees. 145 00:11:03,750 --> 00:11:05,430 So here's a few examples. 146 00:11:06,450 --> 00:11:12,210 I go ahead and I've made an executable called input out an executable or a binary, depending on the 147 00:11:12,210 --> 00:11:12,870 system you're on. 148 00:11:12,870 --> 00:11:15,300 This is input out because I am using Bash. 149 00:11:17,060 --> 00:11:20,240 And you noticed that this one looks OK, right? 150 00:11:20,420 --> 00:11:24,950 I enter a label, I then a space, then within a space, then a height. 151 00:11:25,370 --> 00:11:30,400 Then it says the area of rectangle B, which is the label, is eighty eight times ten. 152 00:11:30,410 --> 00:11:31,370 That makes sense, right? 153 00:11:32,000 --> 00:11:36,020 However, these other ones don't make a ton of sense, so let's talk a bit about that. 154 00:11:36,380 --> 00:11:44,300 So most people would probably think that the a user would see this program and they would just be like, 155 00:11:44,300 --> 00:11:49,280 Oh, I'm going to enter things in the order that they have mentioned here label width, height. 156 00:11:50,030 --> 00:11:56,240 That would be a wrong assumption, though you should never assume that the user is going to follow your 157 00:11:56,240 --> 00:11:59,720 expectations or even your instructions, for that matter. 158 00:12:01,230 --> 00:12:09,120 You should always be on the defense, and most importantly, because hackers can actually intercept 159 00:12:09,120 --> 00:12:15,450 and input that can lead to you not only the crashing of your program based on that input, but also 160 00:12:15,900 --> 00:12:21,180 it could eventually lead to them having control over whatever system your program is running on. 161 00:12:22,230 --> 00:12:27,630 This is something outside the scope of this course, as it's more of a computer security topic. 162 00:12:28,170 --> 00:12:33,270 But yeah, it can be bad if you do not sanitize the user input. 163 00:12:33,270 --> 00:12:40,200 If you do not write code, that makes it makes your program not be so vulnerable to whatever the user 164 00:12:40,200 --> 00:12:40,710 enters. 165 00:12:41,130 --> 00:12:46,080 You should just assume that the user is going to enter any possible thing that could be entered. 166 00:12:46,080 --> 00:12:54,630 So you want to protect against malicious input that could lead to a compromised system or, you know, 167 00:12:54,630 --> 00:12:59,580 just crash your program kind of in less extreme cases. 168 00:13:01,410 --> 00:13:05,370 So what happens if they enter things in the wrong order? 169 00:13:05,400 --> 00:13:09,690 Well, we see right here is not entered in the right order. 170 00:13:09,700 --> 00:13:16,110 We have a integer before the label, which was supposed to be a character and then a character and then 171 00:13:16,110 --> 00:13:18,900 another integer, and we notice that it says the area of the rectangle. 172 00:13:18,900 --> 00:13:19,350 Eight. 173 00:13:20,750 --> 00:13:27,500 Rather than it being rectangle B, and then we see that our answer is zero, what seems strange, then 174 00:13:27,500 --> 00:13:32,540 we have this one here where we got some weird results when a float was used, so eight point seven was 175 00:13:32,540 --> 00:13:35,870 used and that caused the program to also have a result of zero. 176 00:13:36,770 --> 00:13:42,770 Then this one down here, we noticed that there's no spaces in between the user input and in fact, 177 00:13:42,770 --> 00:13:44,510 the program didn't even finish. 178 00:13:45,590 --> 00:13:52,640 And that is because it interpreted this in a certain way in which it thought that it still needs to 179 00:13:52,670 --> 00:13:53,720 collect input. 180 00:13:54,530 --> 00:13:57,340 So that is something we'll look into in the next slides as well. 181 00:13:57,350 --> 00:14:02,180 But here the program is hung up and it is still stalled, waiting for additional input. 182 00:14:04,420 --> 00:14:10,450 So let's specifically take a look at each one of these cases and not only see what's going on, but 183 00:14:10,450 --> 00:14:15,310 what is the keyboard buyer looking like, and then we will break down how the data is being read into 184 00:14:15,310 --> 00:14:17,560 the variables that we created in our program. 185 00:14:20,370 --> 00:14:22,200 So let's look at this top one first. 186 00:14:22,440 --> 00:14:28,620 So this is the one that was actually correct and had a expected result, at least I won't say correct 187 00:14:28,620 --> 00:14:35,820 because that's up to interpretation, whether we provided the correct instructions or not, but it came 188 00:14:35,820 --> 00:14:36,900 out as expected. 189 00:14:37,050 --> 00:14:42,750 The area was 80 and the label was B, so the keyboard buffer is right here. 190 00:14:42,750 --> 00:14:43,800 I have some boxes. 191 00:14:43,800 --> 00:14:48,420 Each one of these boxes kind of represents a character that is being stored on the keyboard buffer. 192 00:14:49,140 --> 00:14:54,480 Down here, I show kind of what we're expecting with each piece of the input. 193 00:14:55,320 --> 00:14:59,130 So first is a B, and that's OK. 194 00:14:59,160 --> 00:15:00,510 That's read in as a chart. 195 00:15:01,110 --> 00:15:07,020 The chart is just expecting one keystroke kind of because a car can just be one character. 196 00:15:07,030 --> 00:15:12,060 Of course, if you look back at the ASCII table, you can notice that most of the things that can be 197 00:15:12,060 --> 00:15:16,320 clicked on a keyboard and pressed on a keyboard are represented there. 198 00:15:18,200 --> 00:15:23,630 So that gets red and it moves on, it has a space separating the char and the next thing, which is 199 00:15:23,630 --> 00:15:24,200 a number. 200 00:15:24,980 --> 00:15:30,140 It reads in this character, but it's supposed to interpret it as an end. 201 00:15:30,800 --> 00:15:35,390 And it does because it's just an eight with a space after it. 202 00:15:35,840 --> 00:15:40,670 And so it reads in this eight and says, OK, an integer eight is being read in. 203 00:15:41,690 --> 00:15:46,200 Then there's a space and then there is a one on the buffer and a zero on the buffer. 204 00:15:46,220 --> 00:15:55,310 And since the integer doesn't discriminate against only having one, you know, against, sorry, I 205 00:15:55,310 --> 00:15:57,710 discriminate against having multiple digits. 206 00:15:58,160 --> 00:16:03,260 You know, an integer doesn't only have to have one digit like the eight, it could have, you know, 207 00:16:03,470 --> 00:16:04,310 tons of digits. 208 00:16:04,310 --> 00:16:09,500 So it sees this one and then it sees this zero and it's like, OK, that's an integer. 209 00:16:09,500 --> 00:16:10,550 And so it reads that in. 210 00:16:11,970 --> 00:16:16,290 And so everything works out, OK, because it was kind of entered in the expected order. 211 00:16:17,910 --> 00:16:19,220 Let's move on to this next one. 212 00:16:19,380 --> 00:16:20,460 So what happens here? 213 00:16:21,870 --> 00:16:28,890 So we have a be entered this kind of the same as the previous slide that begets readiness to cha OK. 214 00:16:29,400 --> 00:16:36,210 And then we have a space, then we have an eight and C++ actually reads this eight and there's an integer 215 00:16:36,210 --> 00:16:39,000 and it's like, OK, eight is an integer. 216 00:16:39,000 --> 00:16:40,110 I'm going to read that in. 217 00:16:40,110 --> 00:16:46,290 But the next thing was a dot, so I'm not going to have that be part of an integer. 218 00:16:48,060 --> 00:16:55,230 So what ends up happening with the rest of this is that scene actually fails on this because it cannot 219 00:16:55,230 --> 00:16:58,830 read the dot and the dot and as an integer. 220 00:16:59,370 --> 00:17:07,830 And so what happens is that it says basically the scene is an object, something that you don't need 221 00:17:07,830 --> 00:17:13,980 to worry too much about that terminology now, but it basically is able to note that it it failed. 222 00:17:13,980 --> 00:17:18,360 And so it sets some sort of status saying that, Hey, I failed. 223 00:17:19,080 --> 00:17:21,300 I failed to read this and something was wrong. 224 00:17:21,900 --> 00:17:28,680 And this is something that can be checked in a similar manner to how we checked for the what the length 225 00:17:28,680 --> 00:17:29,760 was of a string. 226 00:17:30,120 --> 00:17:35,280 Remember how we had like a string variable dot length and then it had parentheses, and I was saying 227 00:17:35,280 --> 00:17:39,330 that it was a length function that can be called on the string. 228 00:17:39,990 --> 00:17:45,510 Similarly, we can call a dot fail function on the scene object. 229 00:17:46,850 --> 00:17:51,710 And so don't get too carried away with the whole function being called an object. 230 00:17:51,740 --> 00:17:56,480 Yet I keep saying over and over again that we will get to this and you're probably pretty antsy for 231 00:17:56,480 --> 00:17:57,470 me to explain it. 232 00:17:58,310 --> 00:18:04,730 But right now, just think of this as being similar to the dot length, except it does something else 233 00:18:04,730 --> 00:18:05,210 for us. 234 00:18:06,110 --> 00:18:10,490 It tells us whether the input stream seen has failed. 235 00:18:10,490 --> 00:18:15,920 So whether encountered something that made it fail or not, this is something that we will be using 236 00:18:15,920 --> 00:18:20,990 in the next lecture where we write some code and we're able to check whether it failed or not. 237 00:18:22,190 --> 00:18:30,050 So at this point, what happens is that there's kind of all this stuff left from the keyboard, but 238 00:18:30,050 --> 00:18:33,280 it failed at this point, and so we're not really going to read it in. 239 00:18:33,290 --> 00:18:36,770 And what happens is that the result just turns out to be zero. 240 00:18:36,770 --> 00:18:42,920 Even though this integer got red in the second integer was not successfully read, and so we didn't 241 00:18:42,920 --> 00:18:44,300 get our expected result. 242 00:18:47,200 --> 00:18:48,470 Let's take a look at this one. 243 00:18:48,490 --> 00:18:53,950 So we have a similar thing, except the eight is the first thing. 244 00:18:54,310 --> 00:18:58,270 Eight is a totally valid character, totally valid char. 245 00:18:58,510 --> 00:19:03,550 You don't have to just have letters, pretty much any keyword press like we were talking about with 246 00:19:03,550 --> 00:19:04,570 the ASCII table. 247 00:19:04,570 --> 00:19:10,430 The AC III table can be considered as a legitimate char. 248 00:19:10,450 --> 00:19:13,000 And so the eight gets read in is a char. 249 00:19:13,000 --> 00:19:16,000 Rather than it being seen as a number, it's seen as a character. 250 00:19:17,080 --> 00:19:18,370 And so it's fine with that. 251 00:19:18,370 --> 00:19:20,550 So the input stream continues. 252 00:19:20,560 --> 00:19:28,300 It has the space, but then it encounters a b and it attempts to process this b by reading it into an 253 00:19:28,300 --> 00:19:30,370 integer process as an integer. 254 00:19:30,760 --> 00:19:32,200 Yet it struggles with that. 255 00:19:32,500 --> 00:19:34,690 And so it actually fails at this point in. 256 00:19:34,690 --> 00:19:43,510 This can be confirmed if you were to use a C and fail to to check it out and see if that was true or 257 00:19:43,510 --> 00:19:43,930 not. 258 00:19:43,930 --> 00:19:48,760 And you would notice that it is in fact true, it did fail if it tries to reel in a B as an integer 259 00:19:49,090 --> 00:19:51,070 and then we still have this leftover stuff. 260 00:19:52,970 --> 00:20:00,520 So the leftover stuff is something interesting that we will talk about in the future as well, probably 261 00:20:00,540 --> 00:20:06,920 the immediate future with either the next election or it's a, you know, immediately subsequent lecture 262 00:20:07,550 --> 00:20:11,510 because stuff can get left on this keyboard buffer. 263 00:20:12,350 --> 00:20:19,010 And then what happens is if you do not clear out the stuff left on this little magical keyboard buffer, 264 00:20:19,640 --> 00:20:24,230 if you try to go to scene something else again. 265 00:20:25,100 --> 00:20:35,750 It's instead of letting you type more stuff as the user is going to just grab whatever's already inside 266 00:20:35,750 --> 00:20:41,480 of this keyboard buffer so you can think of like, whatever the user types, it just stacks up into 267 00:20:41,480 --> 00:20:42,950 this keyboard buffer yet. 268 00:20:44,070 --> 00:20:48,960 If there's something that's already left there, like there's some leftovers, like you can think of 269 00:20:48,960 --> 00:20:55,470 some actual leftovers to be eaten, it'll eat up those leftovers first and read that into your variable. 270 00:20:55,470 --> 00:21:01,170 And that's kind of confusing because if you don't know that there's leftovers, then when you get your 271 00:21:01,170 --> 00:21:07,140 output, you're going to see some stuff that you didn't expect to be there because that's what you get 272 00:21:07,140 --> 00:21:11,430 read in other rather than like what you expect to be read in. 273 00:21:13,640 --> 00:21:16,250 So let's take a look at this last one, what happens here? 274 00:21:16,280 --> 00:21:22,460 Well, there's no spaces, so what happens is that the bigger threat in as a child, even though this 275 00:21:22,460 --> 00:21:26,600 is all smashed up against it, it's like, OK, a car is just one key press. 276 00:21:26,660 --> 00:21:27,350 This is a B. 277 00:21:27,350 --> 00:21:27,890 It's valid. 278 00:21:27,890 --> 00:21:29,690 I read that cars all get to go. 279 00:21:30,440 --> 00:21:35,750 But the second thing is these are the eight and the 10 smashed together. 280 00:21:35,750 --> 00:21:41,720 And honestly, you can't blame C++ too much for this because really, think about it if somebody wrote 281 00:21:42,170 --> 00:21:46,640 eight one zero right next to each other on a piece of paper and then they asked you to explain what 282 00:21:46,640 --> 00:21:47,270 that was. 283 00:21:47,990 --> 00:21:53,810 This can be interpreted in so many ways, but the most obvious thing is that it's the number 810, right? 284 00:21:54,620 --> 00:21:58,070 You're not just going to look at this and be like, Oh, it's for sure. 285 00:21:58,110 --> 00:22:06,290 Eight and then 10, it can be seen as eight, 10 as one number 810, it could be seen as eighty one 286 00:22:06,290 --> 00:22:06,920 and zero. 287 00:22:06,920 --> 00:22:08,930 It could be seen as eight and one and zero. 288 00:22:09,230 --> 00:22:10,850 It can be seen as eight and 10. 289 00:22:11,150 --> 00:22:11,960 All those things. 290 00:22:11,960 --> 00:22:17,360 So you can't really blame C++ for noticing this as one integer eight 10. 291 00:22:17,360 --> 00:22:18,320 And that's what it does. 292 00:22:18,320 --> 00:22:23,270 It actually looks at this buffer at each of these spots, and it considers this one integer. 293 00:22:23,870 --> 00:22:26,240 Well, why does it just stay blank here? 294 00:22:26,240 --> 00:22:29,390 And it does not show my bash prompt again. 295 00:22:29,810 --> 00:22:32,180 That's because the program hasn't finished. 296 00:22:32,180 --> 00:22:33,500 Well, why hasn't it finished? 297 00:22:34,250 --> 00:22:36,560 And that's because it's only read in one integer. 298 00:22:37,010 --> 00:22:43,730 Yeah, in your program, you specified for it to continue trying to read in a second integer after this. 299 00:22:44,390 --> 00:22:47,390 So it's still waiting for that next integer. 300 00:22:47,390 --> 00:22:49,970 And that's why you notice the program has not finished. 301 00:22:50,240 --> 00:22:56,990 You would have to, you know, continue to enter an integer and and or press the enter key. 302 00:22:57,170 --> 00:22:59,870 So that's why that looks like that. 303 00:23:01,740 --> 00:23:03,900 So enough of me explaining this stuff. 304 00:23:04,140 --> 00:23:09,900 Hopefully, though, it was some good graphics to help you understand how the scene really works. 305 00:23:10,380 --> 00:23:14,460 Hopefully, you're also pretty excited that we can make some interactive programs now and that is what 306 00:23:14,460 --> 00:23:20,310 we were going to do in the next video and some of the subsequent videos. 307 00:23:20,580 --> 00:23:26,820 We will be making some more interactive programs messing around with user input, but most importantly, 308 00:23:26,820 --> 00:23:28,260 in the immediate future. 309 00:23:28,260 --> 00:23:34,590 In the next video, we will be trying to see all the ways that you can really mess up with the input 310 00:23:34,950 --> 00:23:39,350 reading and is the wrong data type and stuff like that getting unexpected results. 311 00:23:39,360 --> 00:23:45,750 We're going to kind of suss all that out and throw it out there so you can really see what could potentially 312 00:23:45,750 --> 00:23:47,700 happen when reading and user input. 313 00:23:48,510 --> 00:23:53,070 OK, so with that, go ahead and open your next text editor if you're going to continue on from this 314 00:23:53,070 --> 00:23:53,760 exact point. 315 00:23:54,300 --> 00:23:59,040 Otherwise, if you take a quick break, I will see in the next lecture in whatever text editor you might 316 00:23:59,040 --> 00:24:02,130 like, I'm going to go ahead and use Visual Studio Studio code. 317 00:24:02,130 --> 00:24:04,080 I believe potentially. 318 00:24:04,560 --> 00:24:06,420 But with that, I'll see you in the next lecture.