WEBVTT 00:00.720 --> 00:06.540 Until this point we've only ever had our code in our main. 00:06.810 --> 00:12.310 And I said before that main is what is called a function. 00:12.720 --> 00:15.540 Well we can make our own functions as well. 00:15.540 --> 00:18.950 So let's see how you can do that. 00:18.960 --> 00:29.670 So the very first step always is to declare our function so that anything below can use it. 00:29.780 --> 00:40.010 So we're in cellos are always going to have our declarations above mean usually near the top of the 00:40.010 --> 00:40.900 file. 00:40.910 --> 00:43.570 That's where I like to put them. 00:43.580 --> 00:47.220 So let's take a look at this little bit. 00:47.240 --> 00:53.460 So the first thing you'll see is what is called the return value of a function. 00:53.480 --> 01:03.470 So here it's this weird thing called void and what void means in this case is that there is no return 01:03.470 --> 01:06.280 value for this function. 01:06.350 --> 01:14.230 It doesn't have to be or it could be something like an int or a char or any type you've seen so far. 01:14.630 --> 01:18.710 But we'll talk about return values that later. 01:18.720 --> 01:25.380 So the next thing is the name of the function and we get to choose what that name is. 01:25.380 --> 01:34.880 So this name again remember that it's also an identifier so names have the same restrictions as variables 01:34.880 --> 01:37.180 so you can have a. 01:37.250 --> 01:46.310 So you have to have a letter as the first character but after that it can be digits or letters or underscores. 01:46.310 --> 01:56.540 So for this course our names are always have capital letters as first letter of the function and each 01:56.540 --> 02:00.490 subsequent word will also be capitalized. 02:00.650 --> 02:03.240 But everything else will be lower case like this. 02:05.280 --> 02:09.390 So the next part is the parentheses. 02:09.570 --> 02:14.050 And this indicates the parameters or arguments of the function. 02:14.100 --> 02:19.840 So parameters are variables that can be passed into the function from outside sources. 02:20.420 --> 02:24.060 We'll be looking at this a bit later as well. 02:24.120 --> 02:31.470 So since it's a statement there's always a semi-colon at the end so always remember that this declaration 02:31.470 --> 02:35.140 is a statement. 02:35.210 --> 02:41.110 So this whole line is called a the function signature. 02:41.390 --> 02:49.530 So the function signature consists of the parameters the name of the function and the return type is 02:49.550 --> 02:51.150 the return type. 02:51.360 --> 02:55.070 K. so will be. 02:55.230 --> 03:02.770 You'll see why I say Funt function signature and why a function signature is important in a leader lecture 03:03.150 --> 03:05.900 in this section. 03:05.930 --> 03:10.010 So the next thing we need to do is actually define this function. 03:10.010 --> 03:12.830 So for our definition 03:15.280 --> 03:18.390 we're just kind of say hello. 03:18.550 --> 03:21.860 And notice that I'm rewriting the function signature here. 03:21.970 --> 03:24.420 Same as above. 03:24.700 --> 03:33.890 This K and we have the source code blocker statement block OK. 03:34.280 --> 03:38.790 And this is where we actually define what the code should be for this function. 03:38.780 --> 03:44.080 So all we're going to have here is a hello world that's it. 03:45.850 --> 03:50.930 And so we've defined our function now. 03:59.430 --> 04:04.470 So the last thing to do is just to call the function. 04:04.590 --> 04:10.830 So all we need to do is actually say we don't need the return type anymore more we just have to say 04:10.890 --> 04:18.030 print hello and then pass in whatever parameters we would have which we have none. 04:18.030 --> 04:21.320 In this case and then the semi-colon. 04:21.600 --> 04:22.400 OK. 04:22.720 --> 04:33.150 So Main here its main function is considered the color of the print Telo function. 04:33.180 --> 04:39.770 So just remember that anyone who calls this is what's called calling a function or using the function 04:39.780 --> 04:40.380 right. 04:40.770 --> 04:45.420 So this is what's called calling the function and Main is the caller. 04:45.750 --> 04:48.990 And print hello would be considered the call Lee. 04:49.050 --> 04:59.610 So if you ever hear me say the caller I'm really talking about the caller of the function. 04:59.770 --> 05:02.610 So let's run this and see what happens. 05:03.480 --> 05:06.460 So print out Hello world as we would expect. 05:06.460 --> 05:11.810 So basically we defined our function. 05:13.750 --> 05:24.520 And since Maine is the starting point man calls this function the control flow switches to this print 05:24.520 --> 05:26.360 Telo function. 05:26.420 --> 05:32.330 It does everything it needs to do and the code does all the steps. 05:32.390 --> 05:36.560 There's only one in this case this number 26. 05:36.560 --> 05:47.110 And then this prints hello world and then the control flow shifts back to main and it exits that way. 05:47.220 --> 05:51.630 That's kind of how the flow of function calls work. 05:52.370 --> 05:54.640 It's very important to understand. 05:54.810 --> 06:01.970 And in this case it is very simple and doesn't really do much but it illustrates how functions really 06:01.970 --> 06:11.300 work and so functions are really useful for logically breaking up the code into smaller and easier to 06:11.300 --> 06:12.860 understand chunks. 06:12.980 --> 06:16.330 And we'll be using them basically from now on. 06:16.540 --> 06:21.650 And all of our games will be designed using functions. 06:21.650 --> 06:26.870 So we'll be talking a lot more about functions in the future. 06:27.080 --> 06:31.090 So in the next lecture I want to talk about parameters to functions.