WEBVTT 00:01.070 --> 00:03.150 Allocating memory in code. 00:03.170 --> 00:12.740 So C plus plus defines two operators, the new and the delete operators so that allocate memory from 00:12.740 --> 00:17.330 the free store and release memory back into the free store here. 00:17.840 --> 00:26.300 So the new operator is used with the type to allocate memory and it will return a type pointer to the 00:26.300 --> 00:27.080 memory here. 00:27.080 --> 00:28.540 So let's create one here. 00:28.550 --> 00:29.060 P. 00:33.400 --> 00:40.600 As you can see here, the naive operator will call the default constructor for custom types for every 00:40.600 --> 00:41.980 object it creates. 00:41.980 --> 00:45.880 So the but builtin types, as you know, the integer is builtin type. 00:46.270 --> 00:54.340 This builtin type do not have constructors, so instead a type initialization will occur and this will 00:54.340 --> 00:58.120 usually initialize the object to zero. 00:58.150 --> 01:01.060 In this example a zero integer here. 01:01.060 --> 01:08.020 So in general you should not use memory allocated for built in types without explicitly initializing 01:08.020 --> 01:08.430 it. 01:08.440 --> 01:16.990 So in fact in some ideas, for example, visual cplusplus the debug version of the new version will 01:16.990 --> 01:25.120 initialize memory to a value of zero x CD here in Visual Studio. 01:26.610 --> 01:35.550 So but they they will assign this value hex value to for every byte here. 01:35.670 --> 01:42.420 So as a visual reminder in the debugger that you have not initialized the memory in this case here for 01:42.420 --> 01:49.220 custom types, it is left to the author of the type to initialize allocated memory. 01:49.230 --> 01:56.460 But also it's important too that when you have finished with memory that you return it back to the free 01:56.460 --> 01:59.130 store so that the allocator can reuse it. 01:59.160 --> 02:05.940 You do this by calling the delete operator as shown here. 02:05.970 --> 02:07.680 Delete P. 02:08.910 --> 02:15.000 So when you delete a pointer, the destructor for the object is called here. 02:15.000 --> 02:18.210 So this truck. 02:18.910 --> 02:24.150 There is called so for built in types, this does nothing. 02:24.160 --> 02:30.220 So in this case, because we have integer, it will do nothing because it's built in type. 02:30.220 --> 02:36.580 So it's good practice to initialize a pointer to nullptr here. 02:38.190 --> 02:40.200 No beetles shown here. 02:40.200 --> 02:46.890 So after you have deleted it and if you use the conversion of checking the value of pointer before using 02:46.890 --> 02:47.010 it. 02:47.010 --> 02:50.880 So this will protect your from using a deleted pointer. 02:51.120 --> 03:00.750 And the Cplusplus standard says that the delete operator will have no effect if you delete the pointer 03:00.750 --> 03:04.480 that has value of nullptr. 03:04.530 --> 03:13.320 So as I write here, the delete here is just useless because the P has nullptr if we make it like that. 03:13.320 --> 03:18.840 And as you can see here, the value is never used here because we deleted the P here. 03:19.260 --> 03:25.310 Also, cplusplus allows you to initialize a value at the time you call the new operator. 03:25.320 --> 03:27.960 So here there is a two ways to do it here. 03:27.960 --> 03:32.940 The first is p one new integer. 03:33.620 --> 03:37.580 And 42 in braces here. 03:38.150 --> 03:44.750 The second one, the second example is pretty much the same, but you just use another type of braces 03:44.750 --> 03:46.880 here, Curly braces 42. 03:47.510 --> 03:55.450 So you initialize the new operator and initialize the value of 42 with two different types here. 03:55.460 --> 04:00.080 So for a custom type, the new operator will call a constructor on the type. 04:00.080 --> 04:08.150 So but for built in type, the end result is the same and is carried out by initializing the item to 04:08.150 --> 04:09.350 the value provided. 04:09.350 --> 04:17.330 So you can also use initialize list syntax as shown as well as I will show in next lecture. 04:17.330 --> 04:25.280 So it's important to note that um, initialization is the memory pointed to, not the pointer variable.