32 lines
2.0 KiB
Markdown
32 lines
2.0 KiB
Markdown
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---
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title: Dynamic Memory Allocation
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---
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## Dynamic Memory Allocation in C++
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### What is Dynamic Memory Allocation in C++?
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* **Memory Allocation** in C++ refers to the memory alloted to the variables you use throughout your program.
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* **Dynamic Memory Allocation** is the memory which is alloted to the variables at the run-time and the amount of memory required is also decided at the run-time.
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* This memory comes from **heap**, whereas _non-static_ variables and _local_ variables get memory from **stack**.
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* In C++, the programmer can perform memory allocations manually, and is called as **_dynamic memory allocation_**.
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* It was possible in C to do dynamic memory allocation, by using _calloc_ and _malloc_ functions to allocate memory and using _free_ function to de-allocate the dynamic memory.
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* In C++, in addition to above, there are two functions, _new_ and _delete_ for performing dynamic memory allocation and de-allocation.
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### NEW operator
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* `new` operator can grant the programmer memory from the heap (if available). If the memory which the programmer asks is available, then the `new` operator initializes the memory and then returns the address (reference) of the memory allocated.
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* **Syntax**
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`pointer-variable-type` = **new** `data-type;`
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Example 1: `int *ptr` = **new** `int;`
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Example 2: `int *ptr2` = **new** `int[10];`
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Here, `pointer-variable-type` is a **pointer** of `data type`. The `data-type` can be int, char, etc. or user-defined data-type.
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### DELETE operator
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* It is programmer's responsibility to de-allocate the dynamically allocated memory otherwise the memory would not be available to be re-allocated until the end of the program.
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* To deallocate the memory, `delete` operator is available and can be used by the programmer.
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* **Syntax**
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**delete** `pointer-type-variable;`
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For example to free the memory allocated in example 1 above, we type:
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`delete ptr;`
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Similarly, for example 2, the memory can be freed by:
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`delete ptr2`;
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