WEBVTT 00:01.020 --> 00:11.210 Talk about a similar concept to a raise in that is the concept called C strings C string is a kind of 00:11.210 --> 00:19.340 specialized character array with a very specific difference a C string will always have a known character 00:19.370 --> 00:26.130 at the end of the sequence that no character signifies the end of the string. 00:26.130 --> 00:28.520 So see an example. 00:28.520 --> 00:36.120 So let's say we have a narrator and calling this sir a string. 00:36.250 --> 00:38.470 I'll give it six characters. 00:39.420 --> 00:45.890 OK in going to set them all like this. 00:45.920 --> 00:50.930 So first one capital H. 00:52.730 --> 00:56.530 Next one he 01:00.350 --> 01:15.570 is. 01:15.770 --> 01:22.350 And the last character I'm going to set is actually going to be no character. 01:22.370 --> 01:26.650 So it looks like this 01:29.530 --> 01:33.060 is like Slash 0. 01:34.910 --> 01:41.830 So knows that we need one more character for the word. 01:41.990 --> 01:42.470 Right. 01:42.470 --> 01:48.210 So we always need one more than what how many letters there are in the word. 01:48.330 --> 01:56.270 So is only five characters right but we need six actually have it P A C string. 01:56.270 --> 02:00.900 Otherwise we didn't have this you'd just be a regular character array. 02:03.620 --> 02:07.190 So we can actually do this little bit differently. 02:07.430 --> 02:11.570 And let's say we had this. 02:11.920 --> 02:13.650 Sure. 02:15.160 --> 02:23.540 Another string say and say hello like that. 02:24.020 --> 02:26.820 So now we're using double quotes here. 02:27.080 --> 02:31.730 And also notice that we don't set a null character anyway. 02:32.000 --> 02:40.250 What's happening here is that the another string here points to the first first character. 02:40.580 --> 02:43.120 Each k. 02:43.190 --> 02:47.050 So this is actually pointing to this. 02:47.120 --> 02:52.340 Since this is a pointer this actually points to the very first character. 02:52.340 --> 02:59.670 And notice I also can't steer because we're not going to be able to change it after. 03:00.280 --> 03:03.830 And say we just see out our stuff. 03:03.820 --> 03:05.290 So let's see. 03:05.290 --> 03:06.590 Ouch. 03:06.850 --> 03:08.920 Our array. 03:09.040 --> 03:11.670 See what happens. 03:11.700 --> 03:13.100 Oh hello. 03:17.250 --> 03:26.660 In Whetsel SU output hours another string k. 03:26.770 --> 03:31.590 And also notice that the output Hello up here. 03:31.780 --> 03:35.610 It's not outputting the address like you think it should right. 03:35.810 --> 03:40.340 Like before this is outputting an address. 03:40.330 --> 03:49.410 So you do this can still pending address. 03:49.630 --> 03:59.800 And this is a very special part of C strings where it outputs really what you kind of want it to output. 03:59.810 --> 04:12.300 It doesn't just output the e address outputs the string itself and so here and this another string say 04:12.300 --> 04:13.530 I did this 04:16.690 --> 04:24.100 so that's how you know it's actually pointing to each k because we're actually taking the value pointed 04:24.100 --> 04:30.430 to by another string and it's not outputting the address like it normally would. 04:30.430 --> 04:34.160 It's outputting the actual character itself. 04:35.310 --> 04:41.470 In fact if you do this it just before you know puts the entire string. 04:41.550 --> 04:49.510 And so this is sort of a specialization for a scene out in the insertion operator here. 04:49.710 --> 04:55.140 It's specially per program so output string and not the address. 04:55.160 --> 05:03.320 So one of the reasons why we use this null character is for knowing when to stop when we use pointers 05:03.320 --> 05:05.900 to pass C strings to functions. 05:05.900 --> 05:18.800 So let's see an example of this scatter of all that and what say you had a function we'll call it string 05:18.800 --> 05:26.880 length in and give it a six string is a pointer and not a. 05:26.900 --> 05:28.100 An array here. 05:31.780 --> 05:35.030 It's fine it here. 05:40.890 --> 05:53.200 And an output the return back the link that the strings 8 only 0 starch and or use a different in a 05:53.540 --> 05:56.310 variable air call the 05:59.270 --> 06:14.560 set it to the start of our string and say if the string is not equal to the null pointer right you could 06:14.560 --> 06:20.200 technically pass in null pointer and this would still work fine. 06:20.740 --> 06:33.270 So if it's not we will go through the string using this other pointer and we'll check to see if we have 06:33.270 --> 06:37.320 hit the null character. 06:37.470 --> 06:45.810 OK so we're going to loop until we find that null character Amerson to say length plus plus and are 06:45.810 --> 06:54.810 also going to say P plus plus because we want to go to each character in the array or in this E-string 06:55.250 --> 07:02.450 way that and then all do is return. 07:05.100 --> 07:13.330 And here we will again do another initialization. 07:13.380 --> 07:19.170 So you also do for C strings you can also say something like this. 07:19.170 --> 07:23.870 So again notice we're not using the null character anywhere. 07:23.870 --> 07:31.890 We're just setting it to the string that we want and will figure out that it's actually six characters 07:31.890 --> 07:34.250 not five right. 07:34.380 --> 07:37.450 And C++ will kind of take care of that for you. 07:37.620 --> 07:39.440 For the initialization anyway. 07:41.040 --> 07:43.350 It's the link. 07:46.700 --> 07:52.530 C string Raemer this will output the actual string not the address or anything like that. 07:54.810 --> 07:55.430 It's 07:58.060 --> 08:01.970 called the function string. 08:06.860 --> 08:10.370 Like that. 08:10.960 --> 08:11.680 Run this 08:17.920 --> 08:27.060 from this. 08:27.290 --> 08:32.840 And the link below is five so it's not 6 right. 08:33.010 --> 08:35.620 So which is basically what you want. 08:35.620 --> 08:41.250 You never want to count the last null character because it's always there. 08:41.590 --> 08:45.350 And this had to be conc because this is Konst. 08:45.590 --> 08:57.270 They say you can't have you can't point to a constant pointer if your pointer is not icons as well. 08:57.610 --> 09:06.560 OK so no that we didn't pass the length of the C string here right. 09:06.590 --> 09:09.020 We're not passing any length fear. 09:09.470 --> 09:10.250 OK. 09:10.250 --> 09:19.250 So this really only applies to you see strings because all C strings have to end with this if they don't 09:19.640 --> 09:21.790 then it's just a character array. 09:21.950 --> 09:28.790 And often bad things will happen if you kind of think that it should have the null character but it 09:28.790 --> 09:30.530 doesn't. 09:30.920 --> 09:36.610 So this is really the major difference between C strings and character arrays. 09:36.650 --> 09:39.730 I always have this null the end. 09:39.870 --> 09:43.310 So in the next lecture we'll use practice.