Dynamic Memory Allocation

Dynamic Memory Allocation

1. Active Learning Assignment
Semester : 3
rd
Branch : CE Engineering
Subject : Data Structures(2130702)
Topic : “Dynamic Memory Allocation”
Prepared by : Vaani Pathak
Enrollement No. :170120107131
Guided by : Prof. Ketan Pandya
1Gandhinagar Institute of Technology

2. Introduction to Dynamic Memory
Allocation
•Dynamic Allocation is by which a program can
obtain memory while it is running.
•Pointers provide necessary support for C’s
powerful dynamic memory allocation.
•In general global variables are allocated
storage at compile time. Local variables can
use the program stack.

3. Dynamic Allocation Functions
•1) malloc()
•2)free()
•3)calloc()

4. Malloc()
•It dynamically allocates memory during the
program.
•Prototype of this function is
Void*malloc(size_t, number_of_bytes).
After a successful call, malloc() returns a pointer
to the first byte of the region of memory.

5. Example of Malloc()
•Example:-
Code fragments below allocate 1000 bytes of
contiguous memory.
char*p;
p=(char*)malloc(1000);
Here,(char*)forces void pointer to become a
character

6. Program For Malloc()
#include<stdio.h>
#include<conio.h>
Void main()
{
int n, I, *p, sum=0;
printf(“enter elements: ”)
Scanf(“%f”, &n);
printf(“using malloc \n:”);
p=(int*)malloc(n*size of (int));
if(p==NULL)
{
printf(“Error”);
}
printf(“enter elements of arrays:”);
For(i=0,i<n,i++)

7. …
{
scanf(“%d”, p+i);
sum+=*(p+i);
}
printf(“sum=%d \n”, sum);
free(p);
}

8. Free() Function
•It is the opposite of malloc().
•It returns previously allocated memory to the
system.
•Prototype: void free(void*p);
•It is critical that you never call free() with an
invalid argument. That will delete the free list.

9. Calloc() function
•Calloc() function allocates an amount of
memory equal to num*size.
•It allocates enough memory for an array of
num objects and size bytes long.
•Memory allocated by calloc() is released by
free() function.
•Prototype:
•void*calloc(size_t,n,size_t,number_of_bytes);

10. Example of Calloc()
•Example of Calloc()
•Code fragments below dynamically allocates 100
elements to an integer array.
Int*p;
p=(int*)calloc(100,sizeof(int));
(int*) forces the void pointer to become a integer

11. Program for Calloc()
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
Void main()
{
int, I,n, *ptr, sum=0;
clrscr();
printf(“enter any number:”);
scanf(“%d”, &n);
ptr=(int*)calloc(n size of (int));
if)ptr==null);
{
printf(“!Error”);
exit(o);
}
printf(“enter elements of array:”);
for(i=o;i<n;++i)
{
scanf(“%d”, ptr +1);
sum+=*(ptr+1);
}printf(“sum=%d”,sum);
free(ptr);
Getch();
}

12. Difference between Malloc() and
Calloc()
Malloc()
•In Malloc, how much memory we want we can
pass it as one slot.
•Malloc is faster than calloc.
•Malloc dosnt initializes the allocated
memory.It contains garbage values.

13. …
Calloc()
•We need to split ad pass the memory as we
want.
•Calloc is slower than malloc.
•Calloc initialize the allocated memory to zero.
•Number of arguments is 2.

14. THANK YOU