WEBVTT 00:06.000 --> 00:12.630 Her and pointers are actually related and even interchangeable in some situations. 00:12.720 --> 00:24.660 So I had this example so it Gerais virus that's a blank that betray Ramus five elements and it's going 00:24.660 --> 00:30.050 to put them to even numbers 10 that's 00:33.570 --> 00:37.060 and said I had a pointer as well. 00:39.470 --> 00:46.160 So that no point at the start then I'll do something interesting and I'll say the pointer is a signed 00:46.250 --> 00:47.280 array. 00:48.800 --> 01:01.510 That and if I output value pointed to pointer it's 01:04.280 --> 01:17.510 your like that it's outputting the value of the value pointed to by pointer right. 01:17.540 --> 01:23.790 That the reference operator in phi run this. 01:23.790 --> 01:26.280 It says to is kind of interesting. 01:26.560 --> 01:33.370 So notice that I didn't use the ampersand of this variable k it didn't do this. 01:33.730 --> 01:40.080 And that is because an array is really really is kind of like a pointer in the first place. 01:40.090 --> 01:50.590 So it really what this mind does is it says the pointer is assigned the first element pointed to by 01:50.650 --> 01:52.480 Array k. 01:52.570 --> 02:03.330 So it's equivalent to saying this is a address of the first element k. 02:03.550 --> 02:13.060 These are the same I tend to prefer this because this is quite a bit more explicit and it makes quite 02:13.060 --> 02:14.560 a bit more sense. 02:14.560 --> 02:24.620 So let's actually see an example of this and the address element. 02:25.810 --> 02:28.810 Zero is zero would be the first one. 02:28.810 --> 02:32.250 This one is 02:35.070 --> 02:36.480 so I could say this 02:40.260 --> 02:41.880 and I could also say 02:44.150 --> 02:48.490 it's one it is 02:54.180 --> 02:59.920 the address of Element 1 that way. 03:00.370 --> 03:08.990 And if it run that you'll see that these are identical except for the very last part is 1 0 for element 03:09.290 --> 03:09.950 0. 03:10.040 --> 03:10.830 OK. 03:11.120 --> 03:21.980 And for Element 1 it's 4 and that is because it's 4 bytes offset so 4 bytes because an integer is 4 03:21.980 --> 03:25.390 bytes and it's the next one after. 03:25.480 --> 03:25.830 OK. 03:25.880 --> 03:33.910 So this would be kind of this address and this one would be this address. 03:35.640 --> 03:47.280 When using arrays I tend only to use the index square brackets like this instead of using the array 03:47.280 --> 03:49.400 variable itself. 03:49.460 --> 03:59.730 And so I could I could do this and get the same thing I had before. 03:59.800 --> 04:02.680 So it's offset by 4 right. 04:02.770 --> 04:06.880 It's the address of the next element. 04:06.880 --> 04:14.890 But I tend not to do that because again I think this is a bit more understandable and readable even 04:14.890 --> 04:16.430 though it's a bit more typing. 04:16.690 --> 04:16.940 OK 04:20.900 --> 04:31.250 so we can also use pointers just like arrays just like having this I could do something with this pointer 04:31.280 --> 04:34.560 of 1 to 5. 04:34.870 --> 04:36.530 And if I output 04:38.700 --> 04:49.070 array one Hintz the one that 04:51.730 --> 05:00.130 this should have changed because now the pointer is pointing to this element. 05:00.310 --> 05:06.290 This one has the index at one so it's actually pointing to the second element. 05:06.550 --> 05:11.280 So you should see five being output right here. 05:12.370 --> 05:21.820 So I can I can actually use sort of the array syntax for pointers to. 05:21.880 --> 05:24.440 So that's that's another similarity. 05:24.700 --> 05:26.920 Pointers and arrays share. 05:27.580 --> 05:31.810 So let's another example. 05:32.040 --> 05:35.440 Get rid of all this. 05:36.390 --> 05:36.670 That 05:39.540 --> 05:40.010 in. 05:40.020 --> 05:43.030 Say some equals zero. 05:43.130 --> 05:50.120 A Randy the same example we did in the last lecture and or have pointer as well. 05:53.280 --> 05:59.870 Or And we're going to send it to Erie. 05:59.900 --> 06:09.620 So again this makes the grade point to the first element the three and which do this. 06:09.620 --> 06:17.190 And this makes more sense to me and we'll loop through the whole thing. 06:17.630 --> 06:20.610 Zero less and five 06:24.040 --> 06:30.360 plus plus and we'll get some of them together. 06:30.370 --> 06:33.180 But we're going to use the pointer syntax so that 06:37.350 --> 06:42.060 some this some 06:45.950 --> 06:48.440 can run this. 06:48.570 --> 06:56.390 So some 30 K and notice we're using We're only pointing to the array we're not actually using their 06:56.410 --> 07:05.760 aid directly but in fact it actually went through each one using the pointer and summed the value pointed 07:05.760 --> 07:07.690 to by that pointer. 07:08.010 --> 07:12.700 Each iteration they each index. 07:12.850 --> 07:19.180 And there's another way we could do this could do it like this. 07:19.660 --> 07:22.490 Plus plus that. 07:22.500 --> 07:29.360 So you're in that we also get 30 and exact same thing. 07:29.410 --> 07:34.500 So we're getting the value pointed to by pointer each time. 07:34.500 --> 07:37.770 And then we're actually incrementing a pointer. 07:38.110 --> 07:50.150 So the thing to understand about incrementing is that it will move the pointers. 07:50.540 --> 07:57.590 What it's pointing to by the size of the type that it points to in but it's so it's pointing to an integer 07:57.710 --> 08:03.700 array and integers for bytes so it actually will move the address for bytes. 08:03.710 --> 08:05.340 So then will point to this one. 08:05.540 --> 08:08.100 And then this one and then so on. 08:09.100 --> 08:15.420 So in this example we're pointing to each element of the array using the pointer variable. 08:15.700 --> 08:22.800 So in each iteration we point to the element in. 08:22.810 --> 08:31.890 So for example this one is an int so it would move it by 4 bytes that say the array was a char type. 08:32.050 --> 08:35.560 It would only move it by one byte each time. 08:35.670 --> 08:43.230 So they aren't completely interchangeable though you can't actually increment an array for example. 08:43.270 --> 08:50.270 OK that wouldn't work because you'd be changing the where that array points to. 08:50.280 --> 08:59.120 So say I did this here eight plus plus K doesn't actually work 09:02.020 --> 09:05.580 but it would actually be pointing here which is wrong. 09:05.620 --> 09:05.980 Right. 09:05.980 --> 09:15.050 You kind of want it to always stick to to this first element and you always want it to point to this 09:15.070 --> 09:23.110 first element K because otherwise you'd be sort of offset and it would get confusing and you'd get confused 09:23.140 --> 09:24.490 and bad things would happen. 09:25.290 --> 09:25.890 OK. 09:26.450 --> 09:31.730 So we'll see some more similarities in the next lecture.