WEBVTT 00:00.180 --> 00:06.810 Let's start with violence, one of the most important concepts in programming, and before you learn 00:06.810 --> 00:11.310 what is valuable, please let me explain to you quickly why you need them. 00:11.760 --> 00:16.460 So here is the first program we have written to make an editor blink. 00:16.800 --> 00:22.980 And as you can see, so we need first to initialize the entity by providing the PIN number. 00:23.160 --> 00:25.380 And then when we want to use digital right. 00:25.380 --> 00:27.390 We also need to provide the PIN number. 00:27.720 --> 00:34.470 Look, in this program, whenever you want to change the data center, you use PIN number even when 00:34.560 --> 00:37.490 you need to change these three times. 00:38.070 --> 00:41.550 And this is maybe not the most convenient thing to do. 00:42.160 --> 00:48.180 Also, this program is rather small, but now imagine that you have a program that is one hundred line 00:48.450 --> 00:52.710 long and you need to change that seven times in the program. 00:52.980 --> 00:56.010 Well, this is a quick way to make errors. 00:56.370 --> 01:00.140 So here what we are going to do is we are going to use variables. 01:00.750 --> 01:09.100 So I'm going to create just a viable and then explain what our variables, let's say, into the thing 01:09.420 --> 01:10.710 is equal to 12. 01:11.830 --> 01:13.810 So if I do this. 01:15.020 --> 01:17.720 And I replaced where we've been. 01:19.350 --> 01:26.650 All right, now, if I want to change the editing, I just need to change it once here. 01:27.090 --> 01:27.390 OK? 01:27.420 --> 01:34.180 And whenever I write any dippin the value here, so it will be replaced by 12. 01:34.440 --> 01:35.470 OK, so no effect. 01:35.490 --> 01:37.980 But even I have the same program. 01:38.160 --> 01:40.250 But using the pin Edvin. 01:40.650 --> 01:48.930 So what is a viable viable represents the stored value that you can reuse later in your program. 01:49.320 --> 01:55.820 It's kind of a container and to make it easier to recognize it, you can give it to name. 01:56.250 --> 01:58.160 So I'm going to create a new find. 02:01.270 --> 02:09.010 And I'm going to create viable here to create a viable first, you need to give a type of data type. 02:09.010 --> 02:12.610 So among the most common data type, you have it. 02:12.610 --> 02:15.280 And you can see when I put it, you have the column. 02:16.210 --> 02:19.910 So it means integer and it is a round number. 02:19.930 --> 02:27.060 So, for example, zero one, two, three, but also in the negative like minus five, minus 10, etc.. 02:27.190 --> 02:29.270 So now you need to be the name. 02:29.290 --> 02:35.540 Let's put a fono and a semicolon to declare the variable. 02:35.560 --> 02:37.510 So there are actually two steps. 02:37.510 --> 02:44.890 When you create a viable first, you need to declare eight and then you can initialize it so you can 02:44.890 --> 02:46.210 give it a value. 02:46.450 --> 02:47.950 So let's say but seven. 02:48.550 --> 02:54.420 OK, and I don't forget the semicolon after initialized available here, I declare a viable. 02:54.430 --> 02:55.510 There is no value in it. 02:55.780 --> 02:59.640 And here I initialize the variable that was declared previously. 02:59.890 --> 03:08.830 I can also initialize the variable in the setup and if I want, I can directly also initialize the variable 03:08.950 --> 03:09.370 here. 03:09.850 --> 03:13.950 So here I declare and I initialized available at the same time. 03:14.200 --> 03:15.370 And what will happen here? 03:15.400 --> 03:21.970 So first, the lines on the top of the program will be basically where you declare your valuables. 03:21.990 --> 03:23.680 So this will be executed first. 03:23.950 --> 03:29.920 And then, as you know, the void set up would be executed and then the loop would be executed forever. 03:30.490 --> 03:37.980 So what will happen in this case is first we create a viable so we declare a and we initialize a two 03:37.990 --> 03:38.550 five. 03:38.860 --> 03:40.600 Not when we enter the setup. 03:41.080 --> 03:43.330 We simply change the value inside. 03:43.330 --> 03:47.410 A valuable is not a constant value unless you specify it. 03:47.440 --> 03:50.950 It's a container where you can change the value at any moment. 03:51.230 --> 03:53.770 Of course, you need to make sure this is the same data type. 03:53.770 --> 03:54.780 So integer. 03:55.120 --> 03:59.410 So let's for example, let's do that begin. 04:01.930 --> 04:09.430 OK, with nine thousand six hundred, so print and then and yeah, before we have just printed some 04:09.430 --> 04:16.630 text, but you can directly put the name of a valuable and this will print the name of the label. 04:16.630 --> 04:19.450 So let's name this program violence. 04:21.710 --> 04:27.350 OK, and make sure you already know is correctly connected, and now if I open the science monitor, 04:27.620 --> 04:35.990 I will see the value seven, OK, because A was equal to five first and then I changed the value inside 04:35.990 --> 04:40.420 A and I print an A whenever you use the name of available. 04:41.030 --> 04:47.540 What we really happen in the program is that the name of the variable will be replaced what we call 04:47.540 --> 04:57.500 evaluated to its value, which is said you can also use operators like plus minus etc. to put a value 04:57.500 --> 04:57.920 inside of. 04:58.320 --> 05:03.650 So not like this, we should see a equal to even. 05:05.080 --> 05:12.430 OK, so now A is equal to error, and you can also use a viable to create another viable, let's say, 05:12.430 --> 05:13.330 create another one. 05:13.330 --> 05:15.310 So I could create that. 05:15.310 --> 05:17.620 I'm going to create the I could create it here. 05:17.620 --> 05:19.480 So declare it here, for example. 05:19.930 --> 05:26.770 And then but B is equal to, let's say A plus or OK. 05:26.770 --> 05:28.300 And let's print the. 05:30.150 --> 05:38.550 So now A is equal to anyone at this line, and B will be equal to A plus false or B will be equal to 05:38.550 --> 05:39.300 15. 05:39.600 --> 05:46.550 So you can combine variables together and note that whenever you write a viable source, you write a 05:46.710 --> 05:49.590 A will be evaluated to its last value. 05:49.600 --> 05:53.870 So the value it has here and not the value here, OK. 05:53.970 --> 05:58.310 The order of the instructions is very important. 05:58.320 --> 06:05.370 Not if I do this, then you will see that B will not be equal to eight to 15. 06:05.370 --> 06:13.460 Sorry, that will be equal to nine because it was five and five plus four equals nine and then eight 06:13.480 --> 06:13.970 changes. 06:14.610 --> 06:17.460 OK, so that basically is how you use violence. 06:17.460 --> 06:22.880 And we are going to see more about that in the following of this course when we do many activities. 06:23.280 --> 06:27.510 And I briefly talked about constant variables. 06:27.510 --> 06:29.000 What are constant variables? 06:29.010 --> 06:33.960 Well, as you can see, a variable is a continuum where you can change the value at any time. 06:34.380 --> 06:39.060 But maybe you want to create some variables where the value can't be changed. 06:39.270 --> 06:40.710 And why is that, for example? 06:40.720 --> 06:46.370 Well, at the beginning of this lesson, I used available to store the PIN for analogy. 06:46.710 --> 06:52.470 And the thing is that once you have put the pin for the eight, it's been twelve in your program. 06:52.470 --> 06:55.570 You're not going to change it while you're on the program, OK? 06:55.650 --> 06:58.280 When you run the program, the hardware set up doesn't change. 06:58.530 --> 07:00.960 So in this case, you will use constants. 07:00.960 --> 07:03.690 So there are different ways to create constants. 07:03.690 --> 07:09.540 But here what I'm going to do is to use define so hashtag and define. 07:09.990 --> 07:12.150 You can see here it should turn green. 07:12.690 --> 07:20.010 OK, and then the convention to create variables which are constant is to use all the keys. 07:20.310 --> 07:30.000 But it's been so all keys and separate the world with and underscore and then you put the value, you 07:30.000 --> 07:31.720 don't put an equal sign. 07:31.740 --> 07:32.970 OK, this is different. 07:32.980 --> 07:40.820 So I shouldn't define the name of the variable in either case, the value of the value. 07:41.250 --> 07:43.800 And now you can use that in your program. 07:43.800 --> 07:48.330 And if you try to modify this, this simply won't work. 07:48.840 --> 07:53.010 OK, so you have normal variables and variables that you don't want to change in your program. 07:53.430 --> 08:00.180 So to quickly recap here, a valuable is a container you can use to store a value so that you can reduce 08:00.180 --> 08:06.510 that value later in your program to create a viable without when you first need to declare it with a 08:06.510 --> 08:13.290 name and a data type, then you can give it any value so you can initialize it here and give it any 08:13.290 --> 08:19.740 value all along your program, just making sure that the value stays in the data that you have chosen 08:20.040 --> 08:22.800 and you can create constant viable like this.