1 00:00:00,060 --> 00:00:00,780 Welcome back. 2 00:00:00,810 --> 00:00:06,510 In this video, we are going to look at another control, which is one type of a loop, and there are 3 00:00:06,510 --> 00:00:08,010 multiple types of loops. 4 00:00:08,430 --> 00:00:11,220 And we're going to start with a while loop. 5 00:00:11,220 --> 00:00:17,860 So a while loop executes a block of code repeatedly as long as a given condition is true. 6 00:00:18,120 --> 00:00:20,680 So we're looking at this wild, key word. 7 00:00:20,850 --> 00:00:26,550 Then we have a condition in the brackets, in the square brackets and then in the curly brackets. 8 00:00:26,550 --> 00:00:30,660 We have the code that should be executed as long as the condition is true. 9 00:00:31,320 --> 00:00:36,460 So now if we look at the specific example, it could look like this. 10 00:00:36,480 --> 00:00:40,550 So we have a variable called X and it should be one. 11 00:00:40,560 --> 00:00:42,150 So it starts with the value of one. 12 00:00:42,510 --> 00:00:49,170 And then we compare and say as long as X is less or equal to 10. 13 00:00:50,620 --> 00:00:52,880 We want to execute the following code. 14 00:00:52,900 --> 00:00:59,410 We want to say X, so we should just print the value of X, nothing more than that. 15 00:01:00,340 --> 00:01:07,090 All right, so if we do it like this, then we get an infinite loop, because this wild statement will 16 00:01:07,090 --> 00:01:12,960 always be true because one is always less than 10 or equal to 10. 17 00:01:13,480 --> 00:01:20,880 So what we need to do is we need to at one point lead to an end for this condition. 18 00:01:20,890 --> 00:01:23,560 So this condition has to end at one point. 19 00:01:23,570 --> 00:01:24,480 It's really important. 20 00:01:25,030 --> 00:01:31,800 It can either be done through whatever happens within the wire loop or it can be done from outside. 21 00:01:31,810 --> 00:01:39,070 So let's say we execute something as long as the mouse is moving, as soon as the mouse is not moving 22 00:01:39,070 --> 00:01:40,630 anymore, we don't execute it. 23 00:01:41,440 --> 00:01:46,240 This is a very basic example and this is something that probably shouldn't happen. 24 00:01:46,450 --> 00:01:55,780 But if you look at our mouse while we're moving it, it's also changing its position and our UI, even 25 00:01:55,780 --> 00:02:00,490 though, of course, it will not be executed via a wire loop, how the mouse is displayed. 26 00:02:00,490 --> 00:02:08,500 But it's going to be something that really is calculated all the time, meaning our screen so refreshing 27 00:02:08,500 --> 00:02:12,760 the whole screen and displaying the position of the mouse at a specific point. 28 00:02:13,330 --> 00:02:13,680 All right. 29 00:02:13,690 --> 00:02:19,500 So this while Loop will be executed all the time until the point where the condition is not true anymore. 30 00:02:19,540 --> 00:02:28,030 So we need to actively lead to an end of this condition, meaning that we can do something such as incrementing 31 00:02:28,030 --> 00:02:31,250 X each time that this while loop is executed. 32 00:02:31,480 --> 00:02:38,560 So what will happen now is our X is one in the first iteration, then this condition is checked. 33 00:02:38,570 --> 00:02:40,840 So is one less or equal ten. 34 00:02:41,230 --> 00:02:41,900 It's true. 35 00:02:41,920 --> 00:02:43,980 So execute the code block. 36 00:02:44,440 --> 00:02:50,110 And in the globe -- is just going to print X, whatever X is in our case one, and then it's 37 00:02:50,110 --> 00:02:55,270 going to increase X by one, which means that in the next iteration is going to be two. 38 00:02:55,600 --> 00:02:59,320 So we check is two less or equal ten. 39 00:03:00,010 --> 00:03:00,630 It's true. 40 00:03:00,640 --> 00:03:01,060 All right. 41 00:03:01,070 --> 00:03:02,530 So please execute the code. 42 00:03:02,920 --> 00:03:07,360 So it's going to print two and increment X by one. 43 00:03:07,630 --> 00:03:13,480 So it's going to be three in the next iteration and that's how it's going to go until it's a ten. 44 00:03:13,510 --> 00:03:16,150 So it's going to check ten less equals. 45 00:03:16,150 --> 00:03:17,370 Ten is true. 46 00:03:17,740 --> 00:03:18,190 All right. 47 00:03:18,200 --> 00:03:25,050 So execute the block, print ten, increase X by one, which means X is going to be eleven now. 48 00:03:25,060 --> 00:03:28,650 So we check is 11 less or equal ten. 49 00:03:29,080 --> 00:03:29,880 No, it's not. 50 00:03:29,890 --> 00:03:35,360 So don't execute the block any more, but go to the next line of code, whatever that will be. 51 00:03:35,380 --> 00:03:43,840 So if we have something here while loop is done only then this while loop is done, code will be executed. 52 00:03:45,520 --> 00:03:53,050 So let's execute this code and we see one, two, three, four and so forth, five, six, seven, eight, 53 00:03:53,050 --> 00:03:53,710 nine, ten. 54 00:03:53,920 --> 00:03:55,270 And while loop is done. 55 00:03:56,600 --> 00:04:01,850 Now, if you want to print them next to each other and not line by line, you can, of course, instead 56 00:04:01,850 --> 00:04:08,300 of writing print and just print it and it will print it just next to each other. 57 00:04:11,020 --> 00:04:15,100 So the we are one, two, three, four and four, why is that? 58 00:04:16,560 --> 00:04:24,180 Now, by the way, what if you want this while loop to be in the next line, so this texture while loop 59 00:04:24,180 --> 00:04:24,600 is done? 60 00:04:25,110 --> 00:04:29,730 Well, how you can do it is you can add an additional line break manually. 61 00:04:30,150 --> 00:04:30,960 How would you do that? 62 00:04:30,990 --> 00:04:39,240 Well, you do a backslash and here this backslash and is not going to be interpreted as an RN and as 63 00:04:39,240 --> 00:04:46,230 a string, but it's just going to say or it's going to be interpreted as a code, so to speak, and 64 00:04:46,590 --> 00:04:48,380 it's going to create a line break. 65 00:04:48,720 --> 00:04:50,330 So as you can see, it's also orange. 66 00:04:50,340 --> 00:04:55,710 It's not green as the string is, and that's generally what the backslash does. 67 00:04:56,040 --> 00:04:58,530 It escapes the character. 68 00:04:58,530 --> 00:04:59,720 So that's the key word here. 69 00:04:59,730 --> 00:05:07,230 It says escapes or escapes the end, which means that it will be ignored as a string, but it will be 70 00:05:07,500 --> 00:05:10,380 used as code, so to speak. 71 00:05:11,040 --> 00:05:18,030 So if we run that again, then while Loop is done, will be on the next line of code or on the last 72 00:05:18,030 --> 00:05:25,550 line of this case of our console, you can also see that this empty space here is also over here. 73 00:05:25,650 --> 00:05:29,880 So you can even get rid of this empty space and it will still work. 74 00:05:31,580 --> 00:05:35,980 So that we are now there is no empty space at the start of the line anymore. 75 00:05:37,700 --> 00:05:45,350 So now a little challenge for you, right a while loop, which only prints every second value descending 76 00:05:45,590 --> 00:05:47,350 from 100. 77 00:05:47,990 --> 00:05:53,360 So it's going to print 98, 96, 94 and so forth. 78 00:05:53,760 --> 00:05:54,140 All right. 79 00:05:54,150 --> 00:05:55,490 So please go ahead and try that. 80 00:05:57,080 --> 00:06:01,130 All right, I hope you tried it, so we started one hundred and. 81 00:06:02,170 --> 00:06:04,300 We go down to zero. 82 00:06:05,190 --> 00:06:10,260 And then instead of plus plus we say minus equal to. 83 00:06:11,620 --> 00:06:12,880 All right, now it's going to print. 84 00:06:13,920 --> 00:06:21,570 The value and it's going to go down by two each time, and maybe we even started well, this in this 85 00:06:21,570 --> 00:06:22,950 case 100 will be included. 86 00:06:23,280 --> 00:06:28,530 Otherwise, what we could do is go from ninety nine here. 87 00:06:28,690 --> 00:06:30,630 But I said going from 100. 88 00:06:30,640 --> 00:06:33,630 So let's just see what is going to print. 89 00:06:34,020 --> 00:06:40,020 And we are one hundred ninety eight ninety six ninety four, 92, 90, 88 and so forth. 90 00:06:40,270 --> 00:06:43,290 So it goes all the way down to. 91 00:06:44,790 --> 00:06:46,080 Four, two and zero. 92 00:06:47,560 --> 00:06:52,570 So and these examples, it's a very basic type of code that is executed. 93 00:06:52,600 --> 00:06:55,000 It's really just printing something on the screen. 94 00:06:55,240 --> 00:07:00,140 But this can be super useful and many different applications when writing code. 95 00:07:00,250 --> 00:07:06,100 So while loops are not only useful for what you can see here, what we just print a value onto the screen, 96 00:07:06,100 --> 00:07:10,570 but they're really useful to just execute a code multiple times. 97 00:07:10,870 --> 00:07:15,310 And yeah, that's something that we're going to do quite often in the future and we're going to use 98 00:07:15,310 --> 00:07:16,560 different loop types. 99 00:07:16,560 --> 00:07:24,100 So not just a while loop, but also the for loop or even the do while loop and of course also the for 100 00:07:24,100 --> 00:07:24,670 each loop. 101 00:07:25,120 --> 00:07:30,820 So I'd say let's just go to the next video where we're going to look at the next loop type and we're 102 00:07:30,820 --> 00:07:34,210 going to look through all of them step by step in this course.