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Dynamic memory allocation in C++ language is a powerful feature that allows programmers to allocate memory at runtime. This is especially useful when the size of the data structure is not known at compile time. The C++ language provides operators ‘new’ and ‘delete’ for dynamic memory management. This article explains everything about the Dynamic Memory Allocation in C++ language.
When we execute our program in a computer system. It requires some space to store its instructions,local variables, global variables, and various other functions in C++. It is also known as memory in computers where statements will be stored.
There are two types of memory in our computer system: Static Memory and Dynamic Memory.
We can divide the memory into four parts which are used by the C++ program:
The stack memory stores local variables and function call information. It is based on the LIFO (Last in, First Out) structure, which means that the last piece of data added to the stack is the first one to be removed.
Heap memory, also known simply as the heap, is a region of a computer’s memory used for dynamic memory allocation. It allows memory blocks of arbitrary sizes to be allocated and deallocated at any time.
We can classify memory into types: static memory allocation and dynamic memory allocation. Understanding these types helps in efficient memory management and ensures the optimal performance of C++ programs.
Dynamic memory allocation in C++ is a powerful feature that allows for flexible and efficient memory management at runtime. Let’s examine some reasons why dynamic memory allocation is commonly used in the C++ language.
Operating systems use static memory for allocation for normal data types in C++. For example, int r, double arr[30], char name [30], etc. int r, double arr[10]; char name[20]; etc. This memory is allocated automatically at compile time and de-allocated when the function block or program finishes by the operating system. The operating system uses the dynamic memory allocation for dynamically allocated variables in the program. For example, int *ptr = new int. This memory must be deallocated by the programmer when it is no longer required. Because memory leaks occur when the programmer forgets to deallocate the memory.
Dynamic memory allocation is a crucial concept in C++. It allows the creation of objects and arrays whose size is not known at compile time but determined at runtime. In this situation, we can use the ‘new’ operator in the C++ language, which allocates memory at runtime.
Syntax of ‘new’ operator
The following program demonstrates the ‘new’ operator in C++:
Program
Output
Syntax
Example C++ Program
Output
In C++ language, the ‘delete’ operator is used to deallocate memory that was previously allocated using the ‘new’ operator. When you allocate memory dynamically, it resides on the heap or free store, and it’s your responsibility to free this memory when it’s no longer needed to prevent memory leaks.
Syntax of ‘delete’ operator
Syntax to delete an array of memory
The following program demonstrates the delete program
Program
Output
The new operator can also allocate a block of memory (an array) of any data type.
Syntax
Example
char *name = new char[30]
In C++ language, We can declare in two primary ways, using standard array declarations and the ‘new operator. Each method has its own use cases, advantages and limitations. Here’s a detailed comparison of the two approaches:
Feature | Standard Array Declaration | Using ‘new’ Operator |
Size | The fixed, known at compile time | Dynamic, determined at runtime |
Memory Allocation | Stack | Heap |
Deallocation | Automatic | Manual(using delete[]) |
Flexibility | Limited to compile-time size | Flexible, runtime size |
Performance | Faster Allocation | Potentially slower due to heap management |
The following program with a new operator in C++:
Program
Output
In the C++ language, we can also allocate dynamic memory for objects. When we create an object of a class, a constructor function is invoked. A constructor is a member function of a class that is used to initialize the object.
The following program demonstrates the dynamic memory allocation in C++:
Program
Output
Let’s understand the malloc() , calloc() and free() library function definition before moving forward:
C Functions | Definitions | Syntax |
malloc() | This function is used for dynamic memory allocation. This function returns arguments’ size (in bytes) and returns a void pointer to the allocated pointer’s first byte | (cast-data-type*)malloc(size-in-bytes) |
calloc() | The ‘calloc’ function allocates memory for an array of elements, initializes all bytes in the allocated storage to zero, and then returns a pointer to the memory. | void* calloc(size_t num, size_t size); |
free() | This function is used to clear the allocated space (deallocate) from the heap memory. | free(ptr) |
The new operator has similar working as malloc() and calloc() functions. These functions are used to allocate memory during the program execution in C++ and C programs. But when we use a new operator, it invokes the constructor function of the class. But the malloc() and calloc() functions do not invoke the constructor function.
Example C++ Program:
Output
In C++ language, ‘delete’ and free()’ are both used to deallocate dynamically allocated memory. But they have some significant differences. The ‘delete’ is used to deallocate memory that was allocated with ‘new’, and it also calls the destructor of the object, ensuring proper cleanup of resources.
The following program demonstrates the “delete vs free()”:
Program
Output
In this article, we learned about the dynamic memory allocation in C++ language. It is a powerful feature that allows developers to allocate memory at runtime. This provides flexibility in managing memory for various data structures and objects. The ‘new’ and ‘delete’ operators offer a robust mechanism for allocating and deallocating memory, ensuring that constructors and destructors are called, which is essential for resource management and avoiding memory leaks. By understanding these functions, C++ developers can leverage these tools and write more efficient, reliable and maintainable source code.
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