WEBVTT 00:00.690 --> 00:04.860 The Konski word doesn't just apply to normal variables. 00:04.930 --> 00:08.070 You can also use it with pointers and references. 00:08.130 --> 00:20.060 So for example you'd have a pointer to an integer constant like this since say x x 5 and you like something 00:20.060 --> 00:29.950 like this star will say X don't dare calls to X like that. 00:31.750 --> 00:35.430 OK so x pointer points to x. 00:35.430 --> 00:40.700 Now however it can't change the value of x K. 00:40.910 --> 00:44.360 So I can't do something like this 00:47.000 --> 00:47.880 anymore. 00:49.040 --> 01:03.240 Even if we try right it says error read only variable is not assignable So go as read only now. 01:04.010 --> 01:07.680 That means. 01:07.760 --> 01:15.620 So while I can't change the value of what it wants to I can change where it points to. 01:15.770 --> 01:20.060 So I could do something like this. 01:20.630 --> 01:23.520 And why. 01:23.600 --> 01:34.160 And I can do this calls to my. 01:34.390 --> 01:35.700 So that worked. 01:35.710 --> 01:42.920 In fact if I print out the value X pointer value is 01:46.550 --> 01:47.110 ptr 01:51.640 --> 01:52.560 to 50. 01:52.590 --> 01:53.070 Right. 01:53.220 --> 01:56.860 So it's the Y variable. 01:56.910 --> 01:57.210 Now 02:00.350 --> 02:08.050 so and of course I can't change that y variable the variables value. 02:08.880 --> 02:17.190 I can do the complete opposite as well and create a pointer that can change the value but it points 02:17.190 --> 02:24.310 do but not change where points so I can do something like this. 02:24.510 --> 02:26.480 Come in. 02:27.800 --> 02:33.230 Store say Conte's here. 02:34.560 --> 02:46.990 And I'll say Why enter K will give it y it's this. 02:47.050 --> 02:47.340 Now 02:52.310 --> 03:00.960 so if I try to change where y pointer points to 03:03.460 --> 03:04.120 that 03:06.960 --> 03:09.600 try this. 03:09.630 --> 03:10.920 So there you go. 03:10.950 --> 03:15.570 It doesn't I can't change to where it points to 03:19.140 --> 03:29.820 some numbers here that I must set something on on the on the pointer. 03:29.890 --> 03:34.670 So right here I have to set up this here. 03:34.880 --> 03:38.980 And notice also that I can change the value of. 03:40.430 --> 03:43.430 Y going to air. 03:43.760 --> 03:48.920 I mean that's a fire and that's it works. 03:49.050 --> 03:51.030 Doesn't complain to me. 03:51.030 --> 03:51.910 OK. 03:52.620 --> 03:57.510 So we call this a constant pointer. 03:57.510 --> 04:01.920 This one here is effectively like a reference. 04:01.920 --> 04:09.600 In fact it can change what if it can't change what it points to but it can change the value of what 04:09.600 --> 04:18.360 it points to and it is complete opposite of this which can't change the value that it points to but 04:18.360 --> 04:22.080 it can change where points to. 04:22.650 --> 04:33.780 So I always try to read these from left or right to left because that kind of helps me understand how 04:33.780 --> 04:34.960 it works. 04:34.990 --> 04:50.630 So this one is a pointer to an integer constant k and this one is a constant to a pointer that has type 04:50.690 --> 04:56.500 integer k so this is a constant pointer to an integer. 04:59.170 --> 05:05.750 So like I said before the references are basically constant pointers. 05:06.020 --> 05:10.060 So you could do something like this. 05:14.420 --> 05:15.240 Streff 05:19.580 --> 05:33.070 goes to X this ERPs X that k means I can't change where it points to or change its value. 05:33.070 --> 05:33.520 Right. 05:35.780 --> 05:40.610 Because now before references could change the value of X. 05:40.670 --> 05:44.980 However now I can't do that because now it's constant. 05:45.320 --> 05:52.460 K and of course as a pointer this would be like this. 05:55.840 --> 05:58.350 An X pointer to a 06:06.320 --> 06:13.870 these are effectively equivalent terms of what they can and can't do. 06:14.360 --> 06:18.450 So I am using these facts in the next lecture.