C - Dynamic Malloc Function - malloc in C




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C Dynamic malloc() Function - Definition and Usage

  • In C- Programming the malloc () function is used to allocate space in memory during the execution/runtime of the program.
  • malloc () does not initialize the memory allocated during execution,It carries garbage value.
  • malloc () function returns null pointer if it couldn’t able to allocate requested amount of memory.
C Dynamic Malloc Function

C Syntax

malloc (number *sizeof(int));     
              or    
ptr=(cast-type*)malloc(byte-size)
malloc function c

Example 1

Sample - C Code

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
void main()
{
    char *var_memoryalloc;
    /* memory is allocated dynamically */
    var_memoryalloc = malloc( 20 * sizeof(char) );
    if( var_memoryalloc== NULL )  
    {
        printf("Couldn't able to allocate requested memory\n");}
    else
    {
        strcpy( var_memoryalloc,"wikitechy.com");
    }
    printf("Dynamically allocated memory content : " \
            "%s\n", var_memoryalloc );
    free(var_memoryalloc);
    getch();
}

C Code - Explanation

code-explanation-malloc
  1. In this statement we declare the pointer variable “var_memoryalloc” as character datatype.
  2. In this statement we allocate the memory space dynamically.
  3. In this condition we check whether the memory space is empty or not.
  4. In this statement the memory space will be allocated where the content will be assigned for the certain variable.
  5. Here in this statement we print the value of the variable “var_memoryalloc”.
  6. After the process gets completed, we free dynamically allocate memory space.

Sample Output - Programming Examples

code-explanation-malloc-output
  1. Here in this output the dynamic memory will be allocated and the string “wikitechy.com” will be copied and printed as shown in the console window.

Example 2

Sample Code

#include<stdio.h>
#include<stdlib.h>
void main()
{ 
     int n,i,*ptr,sum=0;
     printf("Enter number of elements: ");
     scanf("%d",&n); 
     ptr=(int*)malloc(n*sizeof(int));
     if(ptr==NULL) 
    {
	printf("Sorry! unable to allocate memory"); 
	exit(0); 
    }
    printf("Enter elements of array:");
    for(i=0;i<n;++i) 
    {
	scanf("%d",ptr+i);
	sum+=*(ptr+i);
    }
	printf("Sum=%d",sum);
	free(ptr);
	getch();
 }
malloc function

Output

Enter number of elements :3
Enter elements of array:10
10
10
sum=30

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