Dynamic Memory Allocation in C Programming with Examples

Dynamic Memory Allocation in C Programming

Dynamic Memory Allocation (DMA) allows memory to be allocated at runtime. It is useful when the size of data is not known at compile time.

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Why Use Dynamic Memory?

• Efficient memory usage
• Allocate memory when needed
• Free memory after use
• Useful for large data structures

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Header File Required

#include <stdlib.h>

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1. malloc()

Allocates memory but does not initialize it.

Syntax:

ptr = (type*) malloc(size);

Example:

int *ptr;

ptr = (int*) malloc(5 * sizeof(int));

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2. calloc()

Allocates memory and initializes it to zero.

Syntax:

ptr = (type*) calloc(number, size);

Example:

int *ptr;

ptr = (int*) calloc(5, sizeof(int));

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3. realloc()

Resizes previously allocated memory.

Syntax:

ptr = realloc(ptr, new_size);

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4. free()

Frees the allocated memory.

Syntax:

free(ptr);

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Complete Example

#include <stdio.h>

#include <stdlib.h>

int main() {

    int n;

    printf("Enter number of elements: ");

    scanf("%d", &n);

    int *ptr = (int*) malloc(n * sizeof(int));

    for(int i = 0; i < n; i++) {

        ptr[i] = i + 1;

    }

    for(int i = 0; i < n; i++) {

        printf("%d ", ptr[i]);

    }

    free(ptr);

    return 0;

}

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Important Points

• Always check if malloc/calloc returns NULL
• Always free unused memory
• Avoid memory leaks

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Conclusion

Dynamic memory allocation is essential for advanced C programming. After this, the next topic is Structures in C programming.