Dyanamic Memory Allocation using Malloc Function 💻

Since C is a structured language, it has some fixed rules for programming. One of them includes changing the size of an array. An array is a collection of items stored at contiguous memory locations.

As it can be seen that the length (size) of the array above made is 9. But what if there is a requirement to change this length (size). For Example, If there is a situation where only 5 elements are needed to be entered in this array. In this case, the remaining 4 indices are just wasting memory in this array. So there is a requirement to lessen the length (size) of the array from 9 to 5.

This procedure is referred to as Dynamic Memory Allocation in C. Therefore, C Dynamic Memory Allocation can be defined as a procedure in which the size of a data structure (like Array) is changed during the runtime. C provides some functions to achieve these tasks. There are 4 library functions provided by C defined under <stdlib.h> header file to facilitate dynamic memory allocation in C programming. They are:

• malloc()
• calloc()
• free()
• recalloc()

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C malloc() method

The “malloc” or “memory allocation” method in C is used to dynamically allocate a single large block of memory with the specified size. It returns a pointer of type void which can be cast into a pointer of any form. It doesn’t Initialize memory at execution time so that it has initialized each block with the default garbage value initially.

Syntax:

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

Example:

ptr = (int*) malloc(100 * sizeof(int));
Since the size of int is 4 bytes, this statement will allocate 400 bytes of memory. And, the pointer ptr holds the address of the first byte in the allocated memory.

Code:

#include <stdio.h>
#include <stdlib.h>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main()
{
	int n,i;
	char x='A';
	printf("Enter the no of items to be entered:");
	scanf("%d",&n);
	char *ptr=(char*)malloc(n*1);
	for(i=0;i<n;i++)
	{
	*ptr=x ;
	x++;
	printf("Item-%c,Memory address-%d\n",*ptr,ptr);//ptr is prnting the memory address of x
	ptr++;//increments the memmry adress of x
	}	
	
}

Output: