1 00:00:06,020 --> 00:00:11,060 Everybody what's going on this is Caleb with Debb slopes dot com and in this video we're going to be 2 00:00:11,060 --> 00:00:17,290 talking about how does code work and not how does like a programming language work. 3 00:00:17,300 --> 00:00:20,980 I mean how does code work from the code we write. 4 00:00:20,990 --> 00:00:23,360 How does that actually do what it does. 5 00:00:23,360 --> 00:00:25,160 How does it get down into the computer. 6 00:00:25,160 --> 00:00:31,220 How does it get down into the C.P. you and to actually be processed and perform certain actions or behaviors. 7 00:00:31,220 --> 00:00:32,390 How does code work. 8 00:00:32,390 --> 00:00:36,690 So let's dive right into it with something we'll understand really well. 9 00:00:36,860 --> 00:00:42,080 If you have any experience with programming at all actually so let's begin with source code. 10 00:00:42,080 --> 00:00:48,560 So imagine you've written a source code file a very simple program even hello world that can print out 11 00:00:48,710 --> 00:00:49,370 Hello world. 12 00:00:49,370 --> 00:00:49,600 Right. 13 00:00:49,610 --> 00:00:52,570 That's a program that you yourself wrote. 14 00:00:52,730 --> 00:01:01,100 Now the language that you used whether it's Python javascript swift Objective C C Sharp whatever you 15 00:01:01,110 --> 00:01:08,270 used that's a human readable programming language and we call these high level languages because they 16 00:01:08,270 --> 00:01:11,630 are so easily interacted with by humans. 17 00:01:11,630 --> 00:01:17,600 And they've been they've been abstracted very far away from what a computer processor can actually understand 18 00:01:17,870 --> 00:01:22,200 because obviously a computer processor thinks very differently than a human. 19 00:01:22,490 --> 00:01:28,640 So that's in contrast to low level languages which we'll get to in a moment but high level languages 20 00:01:28,820 --> 00:01:34,100 easy for humans to work with and abstracted far away from the processor. 21 00:01:34,100 --> 00:01:36,220 Low level languages will talk about soon. 22 00:01:36,230 --> 00:01:42,160 So basically you write your source code and then when it comes time to actually run your code and to 23 00:01:42,170 --> 00:01:49,010 build it and to use it we send it into something called a compiler and compilation is basically the 24 00:01:49,010 --> 00:01:57,040 process of taking source code passing it to the compiler and the compiler acts sort of like a translator. 25 00:01:57,050 --> 00:01:57,600 OK. 26 00:01:57,860 --> 00:02:06,230 And what it's going to do is it's going to translate our source code into a lower level language like 27 00:02:06,230 --> 00:02:07,700 machine code or assembly. 28 00:02:07,700 --> 00:02:10,900 Those are two examples of low level languages. 29 00:02:11,000 --> 00:02:16,270 Now I always have this picture of like the United Nations with all those translators with their earpieces 30 00:02:16,340 --> 00:02:22,580 and everything and I think of the compiler as one of those people sitting in the chair helping our source 31 00:02:22,580 --> 00:02:27,000 code be understood by another party right by this CPQ. 32 00:02:27,200 --> 00:02:32,950 And so we need to talk about machine code and assembly what the heck even is that ok. 33 00:02:33,020 --> 00:02:35,270 If you were to look at it you would probably say the same thing. 34 00:02:35,270 --> 00:02:36,640 What the heck is this. 35 00:02:36,650 --> 00:02:43,960 There are different machine code and assembly but they're similar in that they're both low level languages. 36 00:02:44,090 --> 00:02:44,860 OK. 37 00:02:44,930 --> 00:02:50,090 Now basically they both deal with programming the processor directly. 38 00:02:50,090 --> 00:02:54,010 Machine code is usually a stream of binary data. 39 00:02:54,130 --> 00:02:54,410 OK. 40 00:02:54,420 --> 00:03:00,650 Telling the processor to turn on and turn off certain transistors in order to control certain aspects 41 00:03:00,740 --> 00:03:06,590 of the computer or the program that you're using assembly is a low level language. 42 00:03:06,680 --> 00:03:10,430 It's slightly higher the machine code it's not exactly binary. 43 00:03:10,520 --> 00:03:10,850 OK. 44 00:03:10,850 --> 00:03:17,420 There is a layer of abstraction above machine code called assembly but basically assembly utilizes what 45 00:03:17,420 --> 00:03:20,750 are called registers and we'll talk about that more in a second. 46 00:03:20,750 --> 00:03:26,340 But basically they store instructions that control hardware features on the processor directly. 47 00:03:26,350 --> 00:03:33,650 OK so it's like a layer above machine code but it's also not very easily readable and understandable 48 00:03:33,650 --> 00:03:34,510 by humans. 49 00:03:34,570 --> 00:03:40,360 OK thankfully the compiler does a lot of the heavy lifting for us as developers now. 50 00:03:40,460 --> 00:03:46,490 Assembly does have a particular syntax to enable the running of an assembly program so that it knows 51 00:03:46,490 --> 00:03:52,880 when to begin when to and when to jump to a different register pass data perform calculations just like 52 00:03:52,910 --> 00:03:59,990 you would in an ordinary program with no swifter javascript or whatever machine code doesn't have that 53 00:03:59,990 --> 00:04:02,740 machine code literally is binary. 54 00:04:02,750 --> 00:04:07,600 I mean a can be hexadecimal but for the most part it's binary ones and zeros. 55 00:04:07,680 --> 00:04:14,480 OK so thankfully our source code gets translated into assembly language then into machine code and then 56 00:04:14,480 --> 00:04:19,500 finally at the very end it's compiled into an executable code or an app. 57 00:04:19,550 --> 00:04:23,690 If you're building you know apps for the iPhone or even apps for the Mac. 58 00:04:23,750 --> 00:04:30,170 Now I said that we were going to talk about registers and we are this is a really important foundational 59 00:04:30,170 --> 00:04:32,450 piece of the assembly language. 60 00:04:32,660 --> 00:04:40,650 Now basically in assembly you're given between 8 and 32 global variables of a fixed size. 61 00:04:40,800 --> 00:04:46,610 OK so they're global variables they're accessible from wherever and they have a fixed size. 62 00:04:46,760 --> 00:04:48,360 Those are registers OK. 63 00:04:48,380 --> 00:04:54,370 They're simple variables that can hold bits of information and shift them around in the in memory. 64 00:04:54,380 --> 00:05:02,090 Ok now we can work with these to basically store information perform calculations. 65 00:05:02,270 --> 00:05:07,280 We can store particular instructions on how we want the react and respond. 66 00:05:07,330 --> 00:05:13,120 But a real program is going to need a lot more than 30 to one byte variables right. 67 00:05:13,120 --> 00:05:15,790 That's not a lot of data not a lot of information. 68 00:05:15,790 --> 00:05:22,850 So whatever actually does not fit in the registers is stored in memory K or RAM on your computer it's 69 00:05:22,860 --> 00:05:29,470 sort of like like a temporary placeholder in order to put something while you're doing other work. 70 00:05:29,470 --> 00:05:35,230 I kind of like to think of it like you know if you're cooking on on your countertop and you're out of 71 00:05:35,230 --> 00:05:38,910 space you might set some things over on the other counter while you're working. 72 00:05:39,040 --> 00:05:42,640 And then when you're ready for it you might bring it in and use it and then bring other things back 73 00:05:42,640 --> 00:05:43,700 and set them. 74 00:05:43,780 --> 00:05:47,460 You know you want to be able to have extra space to store things. 75 00:05:47,620 --> 00:05:49,030 And that's what RAM is. 76 00:05:49,030 --> 00:05:49,300 Right. 77 00:05:49,300 --> 00:05:54,190 And obviously if you have a little bit of RAM your computer tends to be slower because it runs out of 78 00:05:54,190 --> 00:06:00,760 space and then has to basically handle removing things and putting things in with less space the more 79 00:06:00,760 --> 00:06:04,660 space the less less clogged your system becomes. 80 00:06:04,660 --> 00:06:10,540 So basically what doesn't fit in the registers fits in memory and things and memory are accessed that 81 00:06:10,540 --> 00:06:17,530 particular addresses sort of like we have like a digital neighborhood in our computer that you can access 82 00:06:17,530 --> 00:06:20,760 and machine code basically tells it where to store it where to put it. 83 00:06:20,890 --> 00:06:21,740 And yeah. 84 00:06:21,910 --> 00:06:28,600 So after the compiler does all the heavy lifting and converts our source code into assembly or machine 85 00:06:28,600 --> 00:06:31,630 code it's then compiled into an executable. 86 00:06:31,630 --> 00:06:35,060 Or if you're developing for iOS or Mac an app. 87 00:06:35,100 --> 00:06:41,750 Ok now this executable or this app actually lives on disk on your computer on your hard drive. 88 00:06:41,790 --> 00:06:43,010 K so it's not in memory. 89 00:06:43,060 --> 00:06:44,620 It's stored on your hard drive. 90 00:06:44,710 --> 00:06:50,260 Now it's basically just a box full of machine code and assembly language that's been converted down 91 00:06:50,260 --> 00:06:51,620 from your source code. 92 00:06:51,640 --> 00:06:56,470 So when we run the application the computer is directly told using that machine code what it should 93 00:06:56,470 --> 00:06:56,990 do. 94 00:06:57,160 --> 00:07:01,630 But the cool thing is that we can interact with it physically like we can click a button we can push 95 00:07:01,630 --> 00:07:03,550 a keyboard key. 96 00:07:03,940 --> 00:07:12,160 And that basically can use our input in order to actually tell the C.P. what to do how to display certain 97 00:07:12,160 --> 00:07:15,590 information how to move this here make this noise. 98 00:07:15,610 --> 00:07:19,180 It all boils down to assembly or machine code. 99 00:07:19,180 --> 00:07:21,100 Very very cool stuff. 100 00:07:21,170 --> 00:07:26,830 Now not every application is an app you can click on and interact with sometimes we have to interact 101 00:07:26,830 --> 00:07:28,280 with it through the terminal. 102 00:07:28,390 --> 00:07:32,180 And that's where an executable can be run in a shell. 103 00:07:32,200 --> 00:07:32,800 OK. 104 00:07:32,980 --> 00:07:39,670 Now a shell is just basically a program written by humans that can run other programs and you know you 105 00:07:39,670 --> 00:07:45,280 see your terminal there command line you can type in commands and when I push enter on the keyboard 106 00:07:45,640 --> 00:07:51,370 the cool thing is the operating system is going to basically say hey we need to switch from the shell 107 00:07:51,370 --> 00:07:54,660 program to this computer program that we built. 108 00:07:54,670 --> 00:07:54,910 Right. 109 00:07:54,910 --> 00:08:01,990 Our source code file and it automatically does that for us which is what makes operating system so powerful 110 00:08:01,990 --> 00:08:09,120 and so smart is that they can automatically determine the context for a particular application. 111 00:08:09,160 --> 00:08:13,330 Create new processes and switch them back and forth based on our input. 112 00:08:13,330 --> 00:08:15,550 This is called context switching. 113 00:08:15,790 --> 00:08:21,150 And it's a really powerful feature of an operating system working together with the CPQ. 114 00:08:21,250 --> 00:08:25,760 And so basically from source code we pass it into a compiler. 115 00:08:25,960 --> 00:08:29,830 It's turned into assembly machine code which is basically binary. 116 00:08:29,830 --> 00:08:30,420 OK. 117 00:08:30,640 --> 00:08:36,220 And that then is then compressed down into an executable file which can either be run with direct interaction 118 00:08:36,220 --> 00:08:43,780 from a user like an application or through the terminal in a shell and RCP who is basically going to 119 00:08:43,780 --> 00:08:49,870 take that code and it's going to interact with it and switch back and forth intelligently between all 120 00:08:49,870 --> 00:08:52,360 of the different inputs and everything. 121 00:08:52,360 --> 00:08:55,700 Thanks to our operating system which is a really really cool thing. 122 00:08:55,810 --> 00:09:03,160 So this in essence is how code works are our code gets converted down into binary through multiple layers 123 00:09:03,430 --> 00:09:09,800 of abstraction and that basically allows you to make a program and that's how code works. 124 00:09:09,910 --> 00:09:13,260 It's converted down thanks to compilers and we can run it. 125 00:09:13,420 --> 00:09:18,100 And then the operating system works together with you in order to display what our code is supposed 126 00:09:18,100 --> 00:09:18,820 to do. 127 00:09:18,820 --> 00:09:23,400 Now of course you can write assembly code yourself and do that directly. 128 00:09:23,410 --> 00:09:24,830 Not many people do that though. 129 00:09:25,000 --> 00:09:27,030 And you also can do that with machine code. 130 00:09:27,040 --> 00:09:32,800 But again not one not many people do that because a lot of the things that machine code and assembly 131 00:09:32,800 --> 00:09:37,600 language do can really easily be done with human created programming languages. 132 00:09:37,600 --> 00:09:42,850 It might just be a little less memory efficient and little more resource intensive but very very cool 133 00:09:42,850 --> 00:09:43,530 stuff. 134 00:09:43,540 --> 00:09:48,160 We have a lot to be grateful for as developers that we don't have to write in assembly code or machine 135 00:09:48,160 --> 00:09:49,440 code anymore. 136 00:09:49,450 --> 00:09:50,440 Very very cool stuff. 137 00:09:50,440 --> 00:09:53,550 So let's head over to the next video and let's continue learning. 138 00:09:53,560 --> 00:09:55,350 This is Caleb with devah slopes dot com.