Dynamic Memory Allocation In C Language | Dynamic Memory Allocation In C Language In Hindi | Dynamic Memory Allocation In C Programming Example

Dynamic Memory Allocation in C

Dynamic Memory Allocation is manual allocation and freeing of memory according to your programming needs. Dynamic memory is managed and served with pointers that point to the newly allocated memory space in an area which we call the heap.

Now you can create and destroy an array of elements dynamically at runtime without any problems. To sum up, the automatic memory management uses the stack, and the dynamic memory allocation uses the heap.

The <stdlib.h> library has functions responsible for dynamic memory management.

 

The malloc Function

The malloc() function stands for memory allocation. It is a function which is used to allocate a block of memory dynamically. It reserves memory space of specified size and returns the null pointer pointing to the memory location. The pointer returned is usually of type void. It means that we can assign malloc function to any pointer.

Fig: malloc()

Syntax

ptr=(cast-type*) malloc(byte-size)

Program:

#include<stdlib.h>

int main()

{

int *ptr;

ptr=malloc(15 * sizeof(*ptr));

if(ptr !=NULL)

{

*(ptr+5)=480;

printf(“value of the 6^th integer is %d”, *(ptr*5));

}

}

 

Output:

Value of the 6^th integer is 480

 

The calloc Function

The calloc function stands for contiguous allocation. This function is used to allocate multiple blocks of memory. It is a dynamic memory allocation function which is used to allocate the memory to complex data structures such as arrays and structures.

Malloc function is used to allocate a single block of memory space while the calloc function is used to allocate multiple blocks of memory space. Each block allocated by the calloc function is of the same size.

Fig: calloc()

Syntax:

ptr(cast-type*) calloc (n,size);

 

Program:

#include<stdlib.h>

int main()

{

int  i=ptr,sum=0;

ptr=calloc(10,sizeof(int));

if(ptr==NULL)

{

printf(“error! Memory not allocated”);

exit(0);

}

printf(“Building and calculating the sequence sum of the first 10 terms\n”);

for(i=0;i<10;i=+)

sum+=*(ptr+i);

}

printf(“sum= %d”,sum);

free(ptr);

return 0;

}

 

Output:

Building and calculating the sequence sum of the first 10 terms

Sum=45

The realloc Function

The realloc() function, we can add more memory size to already allocated memory. It expands the current block while leaving the original content as it is. realloc stands for reallocation of memory.

realloc can also be used to reduce the size of the previously allocated memory.

Fig: realloc()

Syntax:

ptr=realloc(ptr,newsize);

Program

#include<stdio.h>

int main()

{

char *ptr;

ptr=(char*)realloc(ptr , 20);

strcat(ptr, “In ‘C’ ”);

printf(“%s,address=%u\n”,ptr,ptr);

free(ptr);

return 0;

}

 

 

The free Function

The memory for variables is automatically deallocated at compile time. In dynamic memory allocation, you have to deallocate memory explicitly. If not done, you may encounter out of memory error.

The free() function is called to release/deallocate memory. By freeing memory in your program, you make more available for use later.

 

Fig: Free()

Program

#include<stdio.h>

int main()

{

int*ptr=malloc(10* sizeof(*ptr));

if(ptr !=NULL)

{

*(ptr+2)=50;

printf(“value of the 2^nd integer is %d “, *(ptr +2));

}

free(ptr);

}

Output:

Value of the 2^nd integer is 50