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Allocating memory in code.

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So C++ defines to operators the new and the delete operators so that allocate memory from the free store

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and release memory back into the free store here.

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So the new operator is used with the type to allocate memory and it will return a type pointer to the

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memory here.

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So let's create an here p.

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As you can see here, the naive operator will call the default constructor for custom types for every

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object it creates.

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So the built in types, as you know, the integer is built and type this boolean type to not have constructors.

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So instead a type initialization will occur and this will usually initialize the object to zero.

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In this example, a zero integer here.

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So in general you should not use memory allocated for built in types without explicitly initializing

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it.

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So in fact, in some ideas, for example, visual C++, the debug version of the new version will initialize

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memory to a value of zero x CD here in Visual Studio.

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So but they they will assign this one hex value to for every byte here.

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So as a visual reminder in the debugger that you have not initialize the memory in this case here for

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custom types, it is left to the author of the type to initialize allocated memory.

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But also it's important to that when you have finished with memory that you return it back to the free

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store so that the allocator can reuse it.

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You do this by calling the delete operator as shown here.

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Delete P.

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So when you delete a pointer, the destructor for the object is called here.

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So this track.

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Third is called.

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So for ten types, this does nothing.

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So in this case, because we have integer, it will do nothing because it's built in type.

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So it's good practice to initialize a pointer to null.

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Peter here.

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No Peter shown here.

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So after you have deleted it and if you use the conversion of checking the value of pointer before using

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it.

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So this will protect your from using a deleted pointer.

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And the C++ standard says that the delete operator will have no effect if you delete a pointer that

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has value of null.

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Peter So as I write here, the delete here is just useless because the P has no.

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Peter If you make it like that and as you can see here, the value is never used here because we deleted

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the P here.

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Also, C++ allows you to initialize a value at the time you call the new operator.

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So here there is a two ways to do it here.

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The first is P one new integer.

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And 42 in braces here.

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The second one, the second example is pretty much the same, but you just use another type of braces

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here called Braces 42.

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So you initialize the new operator and initialize the value of 42 with two different types here.

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So for a custom type, the new operator will call a constructor on the type.

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So but for built in type.

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The end result is the same and is carried out by initializing the item to the value provided.

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So you can also use initialized list syntax as show as will as I will show in next lecture.

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So it's important to note that the initialization is the memory pointed to, not the pointer variable.