WEBVTT 1 00:00:00.080 --> 00:00:03.319 So imagine you are hungry and you ask a friend 2 00:00:03.319 --> 00:00:04.559 to make you a peanut butter sandwich. 3 00:00:04.559 --> 00:00:05.839 Okay, sounds good, right. 4 00:00:05.960 --> 00:00:07.240 You just say, hey, could you whip me up a 5 00:00:07.280 --> 00:00:09.359 PB and J. Yeah, And they just do it. They 6 00:00:09.400 --> 00:00:11.160 know to walk to the pantry, they get the bread, 7 00:00:11.160 --> 00:00:12.119 they unscrew the jar. 8 00:00:12.240 --> 00:00:13.960 Yeah, and they use a butter knife, not a spoon. 9 00:00:14.160 --> 00:00:16.440 It is all entirely seamless. 10 00:00:16.120 --> 00:00:22.440 Exactly because you both share this massive amount of unspoken 11 00:00:22.559 --> 00:00:23.440 human context. 12 00:00:23.559 --> 00:00:26.440 We really do. I mean, we rely on intuition to 13 00:00:26.519 --> 00:00:29.399 fill in the gaps of our communication every single day. 14 00:00:29.640 --> 00:00:33.840 But now imagine asking a painfully literal robot to do 15 00:00:33.880 --> 00:00:36.479 that exact same thing. Oh boy, Yeah, you say, put 16 00:00:36.479 --> 00:00:39.600 peanut butter on the bread. The robot grabs the unopened 17 00:00:39.600 --> 00:00:42.880 glass jar and just smashes it directly into the loaf 18 00:00:42.880 --> 00:00:43.280 of bread. 19 00:00:43.320 --> 00:00:46.280 Crunch, glass and peanut butter everywhere. 20 00:00:45.920 --> 00:00:48.719 Everywhere, because you know, you didn't explicitly tell it to 21 00:00:48.799 --> 00:00:50.119 unscrew the lids, so it didn't. 22 00:00:50.280 --> 00:00:53.520 It is basically the perfect recipe for disaster. When we 23 00:00:53.560 --> 00:00:56.880 try to talk to machines, we realize very quickly just 24 00:00:57.039 --> 00:00:59.679 how much we take our human intuition for granted. 25 00:01:00.039 --> 00:01:00.520 We really do. 26 00:01:00.640 --> 00:01:04.799 Yeah, we speak in generalities, but machines they only understand absolutes. 27 00:01:05.200 --> 00:01:07.719 And that is exactly why you are joining us for 28 00:01:07.760 --> 00:01:10.920 this deep dive today. We are looking at a world 29 00:01:11.159 --> 00:01:13.239 completely devoid of human. 30 00:01:13.040 --> 00:01:15.519 Intuition, a very literal world. 31 00:01:15.439 --> 00:01:18.840 Super literal. The mission for our deep dive is to 32 00:01:18.959 --> 00:01:24.040 explore how humans and machines actually communicate. And to do this, 33 00:01:24.159 --> 00:01:27.560 we're using Steven R. Davis's book CLUS plus for Dummies 34 00:01:27.560 --> 00:01:30.319 seventh edition as our guide today. 35 00:01:30.120 --> 00:01:32.719 Which is great because it serves as a fantastic foundation 36 00:01:32.799 --> 00:01:33.599 for this whole topic. 37 00:01:33.680 --> 00:01:37.439 Absolutely, but just to be clear to you listening, our 38 00:01:37.439 --> 00:01:40.040 goal today is not to have you memorize code or 39 00:01:40.159 --> 00:01:41.120 like learn syntax. 40 00:01:41.319 --> 00:01:43.159 No, we aren't building a mobile app here. 41 00:01:43.079 --> 00:01:46.280 Right, No apps today. Instead, we want to look under 42 00:01:46.280 --> 00:01:50.319 the hood of C plus plus to understand the really fascinating, 43 00:01:50.439 --> 00:01:53.000 highly literal way that computers actually think. 44 00:01:53.079 --> 00:01:55.319 We are going to see how a programming language acts 45 00:01:55.319 --> 00:01:59.000 as this ultimate middleman, you know, translating our messy human 46 00:01:59.000 --> 00:02:02.079 intentions into cold, hard binary reality. 47 00:02:02.200 --> 00:02:04.920 Because the underlying truth of computing is that processes are 48 00:02:04.920 --> 00:02:08.080 incredibly fast, but they are also incredibly stupid. 49 00:02:08.240 --> 00:02:10.360 Right, they do not speak English, They don't understand the 50 00:02:10.360 --> 00:02:11.639 concept of a sandwich. 51 00:02:11.280 --> 00:02:12.439 At all, not even a little bit. 52 00:02:12.759 --> 00:02:16.919 No, they only understand machine language, which is really nothing 53 00:02:17.000 --> 00:02:20.520 more than an endless see of microscopic electrical signals turning 54 00:02:20.520 --> 00:02:22.560 on and off billions of times a second. 55 00:02:22.759 --> 00:02:26.240 Okay, let's unpack this, because if they only speak voltage 56 00:02:26.240 --> 00:02:30.240 and we only speak human language, we obviously need a translator. 57 00:02:30.639 --> 00:02:33.520 We do. It is like we need to draft a 58 00:02:33.639 --> 00:02:40.039 peace treaty for this ultra efficient but painfully literal alien species. 59 00:02:40.400 --> 00:02:43.240 And that, I guess is the role of an intermediate 60 00:02:43.280 --> 00:02:44.800 language like C plus plus N. 61 00:02:45.120 --> 00:02:47.280 That is a great way to put it. You, as 62 00:02:47.319 --> 00:02:49.800 the human programmer, write what is known as a source 63 00:02:49.800 --> 00:02:50.919 file in a text. 64 00:02:50.759 --> 00:02:52.759 Editor, and that looks a bit like English, right, Yeah, 65 00:02:52.800 --> 00:02:53.159 it looks a. 66 00:02:53.159 --> 00:02:55.840 Bit like English combined with some heavy algebra. But the 67 00:02:55.840 --> 00:02:58.599 computer still cannot read that source file. It is still 68 00:02:58.639 --> 00:02:59.159 too human. 69 00:02:59.240 --> 00:02:59.960 So what happens to it? 70 00:03:00.680 --> 00:03:03.639 Well, a specialized program called a compiler has to step 71 00:03:03.639 --> 00:03:04.719 in to bridge that gap. 72 00:03:04.800 --> 00:03:07.080 Okay, I always hear that term compiling. Yeah, but what 73 00:03:07.159 --> 00:03:09.439 is it actually doing mechanically? I mean, it is not 74 00:03:09.680 --> 00:03:11.879 just reading the text aloud to the computer. 75 00:03:12.000 --> 00:03:15.199 No, it is entirely reconstructing it. The compiler takes your 76 00:03:15.319 --> 00:03:19.439 human readable source file and meticulously translates it into object code. 77 00:03:19.599 --> 00:03:20.360 Object code. 78 00:03:20.400 --> 00:03:23.439 Okay, right, but it doesn't stop there. It then performs 79 00:03:23.479 --> 00:03:24.800 a process called linking. 80 00:03:25.039 --> 00:03:26.680 What does linking do think of linking? 81 00:03:26.840 --> 00:03:29.759 Like taking different chapters written by different authors. Maybe you 82 00:03:29.759 --> 00:03:34.280 wrote one chapter and a standard C plus plus library 83 00:03:34.400 --> 00:03:37.360 provided another chapter. Oh I see, yeah, and it binds 84 00:03:37.400 --> 00:03:41.800 them all together into one cohesive, executable book that the 85 00:03:41.800 --> 00:03:44.560 computer's processor can actually open and run. 86 00:03:44.919 --> 00:03:48.800 That makes sense. And C plus plus is uniquely positions 87 00:03:48.800 --> 00:03:50.919 for this kind of heavy lifting, isn't it. Yeah, because 88 00:03:50.919 --> 00:03:53.479 the source mentions it is certified as a ninety nine 89 00:03:53.520 --> 00:03:55.439 point nine percent pure standard. 90 00:03:55.879 --> 00:03:59.240 Yes, and it is considered a low level language. 91 00:03:58.800 --> 00:04:01.000 Which honestly sounds like an insult, like it is less 92 00:04:01.000 --> 00:04:02.039 sophisticated or something. 93 00:04:02.120 --> 00:04:04.280 It does sound bad, But in this world, being low 94 00:04:04.400 --> 00:04:05.879 level is a massive compliment. 95 00:04:06.039 --> 00:04:06.960 Really. Why is that? 96 00:04:07.319 --> 00:04:10.560 Because being low level means it operates very close to 97 00:04:10.599 --> 00:04:13.840 the physical hardware of the computer. There are fewer layers 98 00:04:13.840 --> 00:04:17.319 of abstraction between your code and the actual silicon chips. 99 00:04:17.399 --> 00:04:20.319 Oh wow, so you are right down there near the metal. 100 00:04:20.279 --> 00:04:23.800 Exactly that proximity to the metal is why C plus 101 00:04:23.800 --> 00:04:27.680 plus is heavily used for things where performance absolutely counts, 102 00:04:28.000 --> 00:04:32.560 things like high end video games, graphics, rendering, direct hardware control. 103 00:04:32.680 --> 00:04:34.439 So it is blazingly fast. 104 00:04:34.240 --> 00:04:38.000 Extremely fast, but because it sits so close to the hardware, 105 00:04:38.480 --> 00:04:41.160 it forces the programmer to be incredibly precise. 106 00:04:41.439 --> 00:04:44.560 It demands that precision because, like we said earlier, it 107 00:04:44.600 --> 00:04:46.720 totally lacks that human intuition. Right. 108 00:04:46.759 --> 00:04:49.600 A computer does exactly what it is told, nothing more 109 00:04:49.879 --> 00:04:50.560 and nothing. 110 00:04:50.360 --> 00:04:53.920 Less, and C plus plus enforces this reality through some 111 00:04:54.639 --> 00:04:56.600 incredibly strict grammar rules. 112 00:04:56.360 --> 00:05:00.199 Right, oh, violently strict. For instance, the compiler will completely 113 00:05:00.240 --> 00:05:03.240 ignore all the blank spaces or tabs or empty lines 114 00:05:03.279 --> 00:05:04.040 you put in your code. 115 00:05:04.079 --> 00:05:05.959 Wait, really, even if I format it nicely so I 116 00:05:05.959 --> 00:05:06.959 can read it yep to. 117 00:05:06.959 --> 00:05:09.319 The machine, that is just called white space, and it 118 00:05:09.399 --> 00:05:11.920 just throws it out. It does not care about your formatting. 119 00:05:12.199 --> 00:05:15.399 But it is obsessively strict about capitalization. 120 00:05:15.000 --> 00:05:17.720 Right the case sensitivity, because if you type I int 121 00:05:17.920 --> 00:05:21.360 in all capital letters, it means absolutely nothing to the computer. 122 00:05:21.319 --> 00:05:23.720 Nothing at all. It will just stare at you blankly 123 00:05:24.120 --> 00:05:27.319 and probably throw an error that crashes your entire bills. 124 00:05:27.360 --> 00:05:29.800 But if you type in in all lowercase letters. 125 00:05:30.000 --> 00:05:32.720 Suddenly it understands you perfectly. It knows you are giving 126 00:05:32.720 --> 00:05:34.319 it specific vital command. 127 00:05:34.839 --> 00:05:40.240 That is wild. This strict literal nature really dictates everything 128 00:05:40.279 --> 00:05:41.920 about how we interact with the machine. 129 00:05:41.959 --> 00:05:45.120 It dictates everything. We can't just throw vague concepts or 130 00:05:45.240 --> 00:05:47.319 you know, floating ideas at a processor. 131 00:05:47.439 --> 00:05:48.560 So what do we do instead? 132 00:05:48.680 --> 00:05:51.680 We have to package our data, our numbers, our text, 133 00:05:51.800 --> 00:05:54.879 our logical states. We have to put them into very specific, 134 00:05:55.000 --> 00:05:58.120 rigid containers before the machine will even acknowledge them. 135 00:05:58.279 --> 00:06:00.759 Okay, so if the computer is this pain fully literal 136 00:06:00.800 --> 00:06:04.040 with our commands, how does it handle our actual information? 137 00:06:04.759 --> 00:06:06.839 Well, it uses variables, right. 138 00:06:06.720 --> 00:06:08.800 But if I think about basic algebra, a variable is 139 00:06:08.879 --> 00:06:11.279 just the magic box. You say x equals one, and 140 00:06:11.319 --> 00:06:13.519 then later you can say x equals an entire sentence, 141 00:06:13.839 --> 00:06:15.399 and the math just rolls with it. 142 00:06:15.680 --> 00:06:18.519 Yeah, human math is flexible like that. But C plus 143 00:06:18.519 --> 00:06:21.480 plus does not allow that kind of freedom, not at all. 144 00:06:21.920 --> 00:06:24.439 You have to tell the computer exactly what shape the 145 00:06:24.480 --> 00:06:27.160 box is before you are allowed to put anything inside 146 00:06:27.160 --> 00:06:27.959 it exactly. 147 00:06:28.399 --> 00:06:31.639 C plus plus is what we call a strongly typed language. 148 00:06:31.720 --> 00:06:32.439 Strongly typed. 149 00:06:32.639 --> 00:06:36.199 Yes, every variable is essentially a holding tank and you 150 00:06:36.279 --> 00:06:40.240 must declare the exact type, the exact physical dimensions of 151 00:06:40.279 --> 00:06:42.600 that holding tank in the computer's memory before you ever 152 00:06:42.680 --> 00:06:42.959 use it. 153 00:06:43.079 --> 00:06:45.360 And the most common box is that lowercase T we 154 00:06:45.519 --> 00:06:47.279 just mentioned right, which stands for integer. 155 00:06:47.480 --> 00:06:50.160 Right, whole numbers one to negative fifty. 156 00:06:50.319 --> 00:06:55.160 But relying on integers introduces a massive mechanical flaw. The 157 00:06:55.160 --> 00:06:57.079 book calls it the truncation problem. 158 00:06:57.240 --> 00:06:59.680 Yes, this is where the literal nature of the machine 159 00:07:00.160 --> 00:07:01.480 really bites the programmer. 160 00:07:01.639 --> 00:07:04.199 Let me use a real world analogy to explain how 161 00:07:04.240 --> 00:07:07.240 bizarre this is to you listening. Imagine you are trying 162 00:07:07.279 --> 00:07:10.560 to split three leftover pizzas among three friends. 163 00:07:10.639 --> 00:07:12.160 Okay, you, me and another buddy. 164 00:07:12.319 --> 00:07:16.120 Right, But the accountant managing our pizza party only understands 165 00:07:16.120 --> 00:07:20.279 whole pizzas. They are literally incapable of comprehending a fraction. 166 00:07:20.519 --> 00:07:23.560 They do not have the mental architecture for a slice. 167 00:07:23.240 --> 00:07:26.680 Exactly an integer. Only accountant handling the catering. 168 00:07:26.879 --> 00:07:27.959 That sounds terrible. 169 00:07:28.199 --> 00:07:30.560 It is. So we have three pizzas. I take the 170 00:07:30.600 --> 00:07:33.120 first one and divide it by three people. The account 171 00:07:33.199 --> 00:07:35.519 looks at it and says, one divided by three is 172 00:07:35.600 --> 00:07:38.680 less than one whole pizza. Therefore, the result. 173 00:07:38.399 --> 00:07:40.879 Is zero, and they physically take the slices and throw 174 00:07:40.879 --> 00:07:41.439 them into the. 175 00:07:41.399 --> 00:07:44.360 Trash, right into the trash. You take the second pizza 176 00:07:44.439 --> 00:07:48.920 divide by three, the accountant truncates it again zero into. 177 00:07:48.759 --> 00:07:52.399 The trash, and our buddy does the same thing zero exactly. 178 00:07:52.879 --> 00:07:55.279 We started with three hole pizzas, we divide them up 179 00:07:55.279 --> 00:07:58.720 to eat, and the computer mathematically calculates that we now 180 00:07:58.759 --> 00:08:02.920 have zero plus zero plus zero, which is zero pizzas. 181 00:08:03.040 --> 00:08:06.240 It is infuriating to a human, but it is flawlessly 182 00:08:06.360 --> 00:08:07.639 logical to the machine. 183 00:08:07.720 --> 00:08:09.040 That is so frustrating. 184 00:08:09.199 --> 00:08:12.399 It is if you use integer math in C plus 185 00:08:12.399 --> 00:08:15.680 plus to divide one by three, the fractional part isn't 186 00:08:15.759 --> 00:08:17.920 rounded down, it is simply lopped off. 187 00:08:18.079 --> 00:08:18.920 It just vanishes. 188 00:08:19.160 --> 00:08:22.120 It vanishes into the ether because the integer holding tank 189 00:08:22.240 --> 00:08:25.279 literally has no physical memory space to store a decimal point. 190 00:08:25.319 --> 00:08:27.240 Wait, so if it just throws away the traction, I 191 00:08:27.279 --> 00:08:30.839 am literally losing data every single time I do basic. 192 00:08:30.560 --> 00:08:32.039 Division, every single time. 193 00:08:32.240 --> 00:08:35.240 Why on Earth can't the computer just figure it out? Yeah, 194 00:08:35.320 --> 00:08:37.320 why can't it just see that one divided by three 195 00:08:37.440 --> 00:08:37.879 is a third? 196 00:08:38.080 --> 00:08:40.600 Well, the creators of the language did provide a tool 197 00:08:40.639 --> 00:08:45.120 to handle fractions, but it comes with a significant architectural. 198 00:08:44.519 --> 00:08:46.679 Catch, of course it does. What is the catch? 199 00:08:47.000 --> 00:08:49.879 To store decimals, you have to use a completely different 200 00:08:49.960 --> 00:08:53.440 type of holding tank, a variable type called a float, 201 00:08:53.840 --> 00:08:56.279 which is short for floating point number. 202 00:08:56.159 --> 00:08:58.399 Oh, or you can use its bigger cousin the double 203 00:08:58.519 --> 00:08:59.440 right exactly. 204 00:08:59.720 --> 00:09:03.639 The boxes are specifically engineered to handle the decimal point. 205 00:09:03.720 --> 00:09:06.759 Oh. Perfect problem solve, Then we just use floats for 206 00:09:06.799 --> 00:09:08.720 everything and fire the integer account. 207 00:09:08.840 --> 00:09:12.519 If only were that simple. There is a constant, unavoidable 208 00:09:12.600 --> 00:09:15.840 trade off in computer science between speed and accuracy. Ah 209 00:09:16.000 --> 00:09:20.519 the catch right, Integers are lightning fast. The computer's processor 210 00:09:20.559 --> 00:09:23.840 can crunch millions of integer calculations in the blink of 211 00:09:23.879 --> 00:09:27.480 an eye because they are so simple exactly. Floats require 212 00:09:27.639 --> 00:09:31.200 vastly more computational work. But the real danger isn't just 213 00:09:31.279 --> 00:09:34.639 the speed. It is that floats introduce round off errors. 214 00:09:35.000 --> 00:09:38.519 Round off errors because a computer, as a physical object 215 00:09:38.919 --> 00:09:41.720 doesn't understand the concept of infinity precisely. 216 00:09:42.080 --> 00:09:45.720 Mathematically, one divided by three is point three three three 217 00:09:45.879 --> 00:09:49.279 repeating forever right infinitely. But a computer only has a 218 00:09:49.320 --> 00:09:53.039 finite amount of physical memory. A float variable can only 219 00:09:53.080 --> 00:09:55.799 hold about seven digits of accuracy before it runs out 220 00:09:55.799 --> 00:09:58.200 of space, so it just stops. It stops. It stores 221 00:09:58.240 --> 00:10:01.960 that infinite concept as a very finite three point three 222 00:10:02.120 --> 00:10:04.679 three three three three three. And if you take that 223 00:10:04.759 --> 00:10:06.960 float and multiply it back by three, you do not 224 00:10:07.000 --> 00:10:09.399 get ten. You get nine point nine nine nine nine. 225 00:10:09.519 --> 00:10:12.200 Oh well, think about that. If you are checking out 226 00:10:12.200 --> 00:10:14.399 of an online cart or looking at your banking app, 227 00:10:14.639 --> 00:10:16.200 someone is stealing fractions of ascent. 228 00:10:16.320 --> 00:10:18.120 Yeah, the math just doesn't add up perfectly. 229 00:10:18.320 --> 00:10:20.799 Or worse, if you are calculating the trajectory of a 230 00:10:20.840 --> 00:10:24.360 spacecraft returning to orbit, nine point nine nine nine nine 231 00:10:24.399 --> 00:10:27.480 is not ten. That tiny missing fraction could mean missing 232 00:10:27.519 --> 00:10:28.679 the atmosphere entirely. 233 00:10:28.759 --> 00:10:31.440 It is a real problem. Now, the larger double box 234 00:10:31.480 --> 00:10:32.440 tries to mitigate this. 235 00:10:32.600 --> 00:10:33.559 How much larger is it? 236 00:10:33.840 --> 00:10:36.039 Well, an inbox has a limit of about two billion, 237 00:10:36.320 --> 00:10:40.120 which sounds enormous until you realize modern processors perform billions 238 00:10:40.120 --> 00:10:42.360 of operations every single second. 239 00:10:42.639 --> 00:10:45.159 Right, they chew through two billion instantly exactly. 240 00:10:45.519 --> 00:10:48.759 The double box can hold massively larger numbers, up to 241 00:10:48.840 --> 00:10:50.279 ten to the thirty eighth power. 242 00:10:50.440 --> 00:10:51.879 That is a staggering number. 243 00:10:51.960 --> 00:10:55.840 It is huge. But even the mighty double starts losing 244 00:10:55.919 --> 00:11:00.240 accuracy and generating garbage data after about thirteen or sixteen digits, 245 00:11:00.440 --> 00:11:03.000 you just can't win. You really can. You can have 246 00:11:03.120 --> 00:11:07.039 massive numbers with loose precision or small numbers with type precision, 247 00:11:07.480 --> 00:11:10.440 but the physical limits of memory mean you cannot have both. 248 00:11:10.759 --> 00:11:14.519 So we are basically forced to store our data in 249 00:11:14.559 --> 00:11:18.480 these inherently flawed containers. We have integers that are blazingly 250 00:11:18.519 --> 00:11:22.080 fast but throw away fractions, and floats that are mathematically 251 00:11:22.159 --> 00:11:24.279 precise but slightly inaccurate. 252 00:11:24.440 --> 00:11:26.000 That is the reality of the hardware. 253 00:11:26.039 --> 00:11:28.559 But once you have your data sitting in those flawed boxes, 254 00:11:28.600 --> 00:11:30.279 you have to make them interact. You have to get 255 00:11:30.279 --> 00:11:32.440 the computer to actually make decisions. 256 00:11:32.279 --> 00:11:35.200 And getting a machine to make a logical choice based 257 00:11:35.240 --> 00:11:38.879 on that flawed math is surprisingly dangerous. I can imagine 258 00:11:38.960 --> 00:11:42.600 decision making is what makes a program appear intelligent. You know, 259 00:11:42.639 --> 00:11:46.360 if this specific condition happens, execute that specific command in C. 260 00:11:46.559 --> 00:11:49.559 Plus plus ah. The core of that decision making process 261 00:11:49.679 --> 00:11:52.720 is boolean logic, isn't it, which is handled by a 262 00:11:52.759 --> 00:11:54.840 tiny variable type called bool. 263 00:11:54.720 --> 00:11:58.159 Yes, named after George Boole, the nineteenth century mathematician. 264 00:11:58.399 --> 00:12:01.600 Right, and a bool variable is the simplest box of all. 265 00:12:02.080 --> 00:12:04.879 It can only hold one of two values true. 266 00:12:04.679 --> 00:12:08.279 Or false exactly, though in the early days C plus 267 00:12:08.320 --> 00:12:10.720 plus just use integers to represent this logic. 268 00:12:11.240 --> 00:12:12.120 How does that work? 269 00:12:12.360 --> 00:12:16.000 A zero meant false and absolutely any other number meant true. 270 00:12:16.240 --> 00:12:19.559 Oh that is interesting. That still works under the hood today. 271 00:12:19.679 --> 00:12:22.519 But using the words true and false makes the code 272 00:12:22.600 --> 00:12:23.879 much more readable for humans. 273 00:12:23.960 --> 00:12:24.840 It definitely does. 274 00:12:25.080 --> 00:12:28.240 But here's where that strict, unforgiving grammar comes back to 275 00:12:28.320 --> 00:12:32.320 haunt us. Let's talk about the catastrophic difference between typing 276 00:12:32.360 --> 00:12:35.919 a single equal sign and typing two equal signs. 277 00:12:35.919 --> 00:12:38.840 Oh man, this is a rite of passage. Every programmer 278 00:12:38.879 --> 00:12:41.919 makes this mistake at least once. Really, Oh yeah, A 279 00:12:41.960 --> 00:12:45.279 single equal sign is an assignment operator. It is a command. 280 00:12:45.360 --> 00:12:47.960 A command right, It means take the value on the 281 00:12:48.039 --> 00:12:50.200 right side and violently shove it into the box on 282 00:12:50.240 --> 00:12:50.919 the left side. 283 00:12:50.960 --> 00:12:52.080 Shove it in there, okay. 284 00:12:52.320 --> 00:12:56.080 But two equal signs is an entirely different concept. It 285 00:12:56.200 --> 00:13:00.919 is a question. It means are these two things currently identical? 286 00:13:01.440 --> 00:13:03.639 So if I am writing code for an e commerce 287 00:13:03.679 --> 00:13:06.519 site and I want to ask the computer is the 288 00:13:06.639 --> 00:13:10.759 user's shopping cart equal to zero? But I accidentally use 289 00:13:10.840 --> 00:13:13.559 one equal sign, then you are in trouble because I'm 290 00:13:13.600 --> 00:13:17.480 not asking a question anymore. I am actively emptying their cart. 291 00:13:17.759 --> 00:13:20.000 I am commanding the computer to set their cart to. 292 00:13:20.039 --> 00:13:23.519 Zero, and the compiler will happily execute that command. Even 293 00:13:23.519 --> 00:13:25.720 if you buried it inside an if. 294 00:13:25.440 --> 00:13:26.919 Statement, It just does it. 295 00:13:26.919 --> 00:13:28.960 It views the destruction of the shopping cart as a 296 00:13:29.039 --> 00:13:32.840 highly successful operation. It ruins the entire logic of your program. 297 00:13:32.960 --> 00:13:33.840 That is terrifying. 298 00:13:34.039 --> 00:13:36.519 It is. But even if you master the grammar and 299 00:13:36.639 --> 00:13:39.120 use the double equal sign correctly to ask a question, 300 00:13:39.600 --> 00:13:42.360 you still run headfirst into the math quirks we just discussed. 301 00:13:42.480 --> 00:13:46.200 Oh right, You should virtually never use the equality operator 302 00:13:46.240 --> 00:13:49.519 the double equals to compare two floating point numbers. 303 00:13:49.320 --> 00:13:51.600 Because of the roundoff errors we talked about. Exactly, if 304 00:13:51.639 --> 00:13:55.840 the computer is asking is ten exactly equal to nine 305 00:13:55.879 --> 00:13:59.759 point nine nine nine nine, it will boldly shout false, 306 00:14:01.039 --> 00:14:03.480 even though any human looking at the equation knows the 307 00:14:03.519 --> 00:14:05.200 math was supposed to result in ten. 308 00:14:06.120 --> 00:14:09.279 Exact equality is a total myth when it comes to floats, 309 00:14:09.679 --> 00:14:12.679 because of the microscopic inaccuracies and how they are stored, 310 00:14:12.960 --> 00:14:15.000 you always have to ask if they are close enough. 311 00:14:15.039 --> 00:14:17.000 Close enough, Yeah, you have to write extra code to 312 00:14:17.039 --> 00:14:19.679 check if the difference between the two numbers is incredibly small. 313 00:14:20.000 --> 00:14:21.799 Rather than asking if they match. 314 00:14:21.639 --> 00:14:25.360 Perfectly, that is so tedious. But the way the computer 315 00:14:25.440 --> 00:14:29.000 evaluates multiple logical questions at once is where it gets 316 00:14:29.159 --> 00:14:30.159 genuinely wild. 317 00:14:30.159 --> 00:14:31.519 To me, Oh, you mean short circuiting. 318 00:14:31.720 --> 00:14:35.639 Yes, C plus plus is secretly incredibly lazy. 319 00:14:35.799 --> 00:14:39.000 Well, we prefer to call it ruthlessly efficient. In computer science, 320 00:14:39.039 --> 00:14:40.759 we call this short circuit evaluation. 321 00:14:40.879 --> 00:14:42.879 Okay, let me give an example. Let's say you have 322 00:14:42.879 --> 00:14:45.279 a logical A and D statement. For example, I will 323 00:14:45.279 --> 00:14:47.480 only go outside if it is sunny. A and D 324 00:14:48.000 --> 00:14:49.000 I have my sound glasses. 325 00:14:49.120 --> 00:14:49.639 Makes sense. 326 00:14:49.840 --> 00:14:51.679 Both of those things must be true for the whole 327 00:14:51.679 --> 00:14:52.519 sentence to be true. 328 00:14:52.600 --> 00:14:55.080 Right In C plus plus A, you represent that A 329 00:14:55.159 --> 00:14:57.039 and D with a double Ampersand. 330 00:14:56.879 --> 00:14:59.320 Now if I look out the window and it is 331 00:14:59.399 --> 00:15:03.440 pouring down, that first condition is its sunny. 332 00:15:03.600 --> 00:15:05.440 Yeah is false, completely false. 333 00:15:05.480 --> 00:15:07.679 And because it's an A and D statement, the entire 334 00:15:07.759 --> 00:15:10.120 operation is already ruined. Doesn't it matter if I have 335 00:15:10.159 --> 00:15:13.120 my sunglasses in my pocket or not, I'm not going outside. 336 00:15:13.279 --> 00:15:17.639 And the computer's processor recognizes this inevitability, it does yes, 337 00:15:18.399 --> 00:15:23.240 to save precious microseconds of processing power. If the first 338 00:15:23.279 --> 00:15:26.039 condition in an A and D statement evaluates to false 339 00:15:26.360 --> 00:15:29.440 C plus plus completely ignores the second condition. 340 00:15:29.559 --> 00:15:30.399 It just skips it. 341 00:15:30.399 --> 00:15:32.799 It's short circuits. It refuses to even look at the 342 00:15:32.799 --> 00:15:35.519 rest of the line of code. The same logic applies 343 00:15:35.559 --> 00:15:38.679 to an our statement too. If the first condition is true, 344 00:15:38.759 --> 00:15:41.639 it skips the second one entirely because the overall statement 345 00:15:41.679 --> 00:15:42.639 has already succeeded. 346 00:15:42.840 --> 00:15:46.399 But think about the massive trap hidden in that laziness. 347 00:15:46.480 --> 00:15:49.519 The side effects, Right, What if that second condition wasn't 348 00:15:49.600 --> 00:15:53.320 just checking a value. What if it had actual operational 349 00:15:53.320 --> 00:15:54.600 instructions baked into. 350 00:15:54.440 --> 00:15:56.279 It, like the increment operator. 351 00:15:55.919 --> 00:15:59.039 Exactly, the plus plus which tells a variable to increase 352 00:15:59.039 --> 00:16:00.240 its value by one. 353 00:16:00.279 --> 00:16:02.919 This is a classic example of silent failure. 354 00:16:03.159 --> 00:16:04.159 Explain how that works. 355 00:16:04.519 --> 00:16:07.559 Imagine you write a complex statement that says, is variable 356 00:16:07.559 --> 00:16:10.639 A greater than variable B A and d is variable 357 00:16:10.679 --> 00:16:12.639 C plus plus greater than variable D. 358 00:16:12.840 --> 00:16:15.240 Okay, So if variable A is not greater than b, 359 00:16:15.759 --> 00:16:18.559 the computer stops dead in its tracks. 360 00:16:18.639 --> 00:16:21.759 It never even glances at variable C, which means variable 361 00:16:21.759 --> 00:16:22.960 C never gets incremented. 362 00:16:23.120 --> 00:16:25.559 Never happened if variable C was supposed to be tracking, 363 00:16:25.639 --> 00:16:28.000 like how many times a player tried to log in, 364 00:16:28.080 --> 00:16:31.559 or how many seconds had passed, that data is just gone. 365 00:16:31.639 --> 00:16:32.879 It is lost forever. 366 00:16:33.000 --> 00:16:36.039 The program didn't crash, it just silently failed to do 367 00:16:36.120 --> 00:16:38.759 its job because the computer was trying to save a microsecond. 368 00:16:38.840 --> 00:16:40.679 And this is why we have to ask, how do 369 00:16:40.759 --> 00:16:45.039 you build a stable, reliable digital world when your foundational 370 00:16:45.039 --> 00:16:45.960 tools behave. 371 00:16:45.759 --> 00:16:47.519 This way it seems impossible. 372 00:16:47.600 --> 00:16:50.519 The answer is a philosophy called defensive programming. 373 00:16:50.600 --> 00:16:52.440 Defensive programming, Yeah. 374 00:16:52.240 --> 00:16:54.639 Writing code isn't just about getting the syntax right so 375 00:16:54.679 --> 00:16:57.879 the compiler doesn't throw an air. It is about deeply 376 00:16:57.960 --> 00:17:02.679 anticipating how the machine will stock yiberally lazily optimize your logic. 377 00:17:02.840 --> 00:17:03.919 You have to outsmart it. 378 00:17:04.200 --> 00:17:07.839 You have to actively protect the program from the machine's 379 00:17:07.880 --> 00:17:09.440 own ruthless efficiency. 380 00:17:09.559 --> 00:17:11.559 It's almost like you have to stop thinking like a 381 00:17:11.640 --> 00:17:14.279 human and start thinking like the machine just to control it. 382 00:17:14.400 --> 00:17:15.079 You really do. 383 00:17:15.839 --> 00:17:18.519 And all of that ruthless efficiency, you know, the stript rules, 384 00:17:18.519 --> 00:17:22.440 the flawed math, it all stems from the physical hardware. 385 00:17:22.079 --> 00:17:24.640 Itself, the actual silicon, which. 386 00:17:24.400 --> 00:17:27.880 Brings us to the very bottom layer of our deep dive. Today, 387 00:17:28.519 --> 00:17:31.799 we've talked about how C plus plus translates human logic, 388 00:17:32.480 --> 00:17:35.359 but what is it actually translating into down at the 389 00:17:35.359 --> 00:17:36.079 absolute bottom. 390 00:17:36.160 --> 00:17:37.599 It is translating it all the way down to the 391 00:17:37.640 --> 00:17:39.200 metal to pure binary. 392 00:17:39.400 --> 00:17:43.079 See human math feels so absolute, like a universal law, 393 00:17:43.519 --> 00:17:45.960 but it's totally biological when you think about. 394 00:17:45.720 --> 00:17:46.720 It, very biological. 395 00:17:46.799 --> 00:17:50.000 We count in base ten the decimal system, we use 396 00:17:50.039 --> 00:17:52.559 the digit zero through nine. Why do we do that 397 00:17:53.599 --> 00:17:55.200 because we have ten fingers. 398 00:17:55.279 --> 00:17:58.880 If human beings had evolved with twelve fingers, our entire 399 00:17:58.960 --> 00:18:01.759 mathematical foundation from birth would be base twelve. 400 00:18:01.880 --> 00:18:03.319 That is so weird to think about it. 401 00:18:03.359 --> 00:18:06.519