WEBVTT 00:07.970 --> 00:15.230 In this section we'll be talking about new ways to represent our data by creating our own user defined 00:15.230 --> 00:16.620 types. 00:16.720 --> 00:20.150 We'll leave this off by talking about structures. 00:20.160 --> 00:27.090 Structures are a way of combining multiple different types into one bigger type. 00:27.110 --> 00:34.910 So for example there's no built in book type for C++ but we can make it ourselves and here's how you 00:34.910 --> 00:35.410 do that. 00:35.420 --> 00:40.190 So we say structure which is short for structure and key word. 00:40.560 --> 00:41.320 OK. 00:41.750 --> 00:52.450 And we say the name of our type is going to call a book type and noticed that we have the Brace's here 00:52.540 --> 00:53.400 statement. 00:53.690 --> 01:00.610 We're put a few more some statements inside of each statement block. 01:01.090 --> 01:11.220 And these statements will be the sort of definition of what our book type is composed of OK. 01:11.260 --> 01:17.410 So for example we could have a book ID which is it. 01:17.590 --> 01:24.810 It has a string which is the title of the book. 01:26.140 --> 01:29.590 This is the author 01:34.180 --> 01:40.390 and maybe the year it was published in Libya as well. 01:44.020 --> 01:52.090 So inside this block redeclare all the inner types that make up our structure. 01:52.170 --> 01:57.860 And so that's what that's what these five variables are. 01:58.050 --> 01:58.620 OK. 01:58.750 --> 02:03.510 So each of these variables inside belong to this structure. 02:03.510 --> 02:11.120 In other words and this is really just a way of grouping variables together into our own type. 02:12.360 --> 02:21.130 And remember that this is this is only the declaration of our type and defined by these five. 02:21.420 --> 02:24.320 This case five variables. 02:25.680 --> 02:30.010 But this isn't the this isn't a variable itself. 02:30.120 --> 02:34.810 This whole thing is not a variable it's the declaration type. 02:35.150 --> 02:39.760 So if you want to actually make a variable Here's how you do it. 02:39.770 --> 02:48.850 So this book type like this and we give it in the book say Okay. 02:49.260 --> 03:01.640 So just like we had with like an integer you say book type type and then book as very well me. 03:01.870 --> 03:02.690 OK. 03:03.010 --> 03:09.620 So you can actually access all these members right. 03:09.640 --> 03:16.800 Since we we know we have five member variables of this book. 03:17.020 --> 03:17.680 OK. 03:18.130 --> 03:23.580 So how you access them is through the dot operator. 03:23.620 --> 03:29.560 So you've actually seen it before with seat in but it's not exactly the same thing. 03:30.010 --> 03:31.210 In this case. 03:31.360 --> 03:39.710 So here you say a book in say want to access use e book ID. 03:39.720 --> 03:47.170 So you say a book Dot and will even notice in eclipse that it brings up kind of the completions of what 03:49.000 --> 03:51.760 the member variables are. 03:52.330 --> 03:54.270 The author of book ID. 03:54.700 --> 03:55.890 Oh year. 03:56.320 --> 04:03.460 So let's say one book I read press Enter him and set the book at the king's house. 04:05.670 --> 04:08.520 And we use a function for the 04:11.400 --> 04:24.330 title and author here called Sturr copy which will copy a string into our Auray book title. 04:24.950 --> 04:27.640 Know. 04:28.050 --> 04:28.600 It's 04:31.660 --> 04:40.500 so we're just putting this string literal into the title and copy all of it and even put the character 04:40.620 --> 04:44.850 for a while and then stir up copy 04:49.700 --> 04:50.380 offer 04:53.120 --> 04:59.260 me 100 points you know is Dickins 05:15.790 --> 05:20.930 year a million points you know. 05:21.050 --> 05:22.360 Ouch. 05:23.280 --> 05:30.800 You know nine in price say that's OK. 05:31.090 --> 05:39.790 So the reason the dot operator each time to access the member variable of the book and so in this case 05:39.790 --> 05:47.020 reading all five member variables and all you do is say your variable name that you came up with appear. 05:47.080 --> 05:49.950 And then Dortch whatever. 05:50.150 --> 05:58.980 So our book type really acts like any other type so we could even have you know an array of books and 06:00.710 --> 06:01.380 we want to 06:04.310 --> 06:16.810 Pook's this array of 10 books and actually define them all if you want like books Sphero dot you know 06:18.340 --> 06:19.030 Id 06:22.480 --> 06:23.110 right. 06:23.420 --> 06:27.020 So you could just kind of continue on like that. 06:27.590 --> 06:30.980 So it works just like any other variable. 06:31.000 --> 06:40.330 Or And again structures are a very important feature that help us with our design. 06:40.350 --> 06:40.900 OK. 06:41.050 --> 06:51.250 With our design of our data in fact just like we use functions to design or code we use structures to 06:51.250 --> 06:52.770 design our data. 06:52.960 --> 06:59.090 So often we need to define data in terms of the problem itself. 06:59.200 --> 07:09.140 So for example if we had a library we need books or a in searchers really do help great. 07:09.280 --> 07:20.080 Yes I hope you remember the picture that I showed at the start of the course where we had the transforming 07:20.130 --> 07:22.030 input and output. 07:22.030 --> 07:28.890 This is my mental model of programming while we've been focusing mostly on the kind of transform part 07:28.920 --> 07:29.990 of the algorithm. 07:30.000 --> 07:31.490 Part of it. 07:31.510 --> 07:37.960 Now in this section we'll be really focusing on the input data. 07:40.180 --> 07:46.240 Then we'll talk more about structures and how they can interact with functions in the next lecture.