2. Sreyachandran.v
Sreya.chandran31@gmail.com
www.facebook.com/sreya
twitter.com/username
in.linkedin.com/in/profilename
Stack and Heap

3. Disclaimer: This presentation is prepared by trainees of
baabtra as a part of mentoring program. This is not
official document of baabtra –Mentoring Partner
Baabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt .
Ltd

4. Stack
• Stack is a linear data structure in which a data item is
inserted and deleted at one record.
• A stack is called LIFO(Last In First Out) or
FILO(First In Last Out) structure.
• The first item added to a stack is the last item
removed from a stack.
• Compiler store the local variable inside the stack.

5. Push and Pop
• Writing a value to the stack is called push.
• Deleting a value from stack is called pop.

6. #include <stdio.h>
int hcf(int n1, int n2);
int main()
{
int n1, n2;
n1=24;
n2=16;
printf("H.C.F of %d and %d = %d", n1, n2, hcf(n1,n2));
return 0;
}
int hcf(int n1, int n2)
{
i f(n2!=0)
return hcf(n2, n1%n2);
else
return n1;
}

7. 1.main()
n1=24
n2=16
2.hcf(24,16)
3.hcf(16,24%16)=hcf(16,8)
4.hcf(8,16%8)=hcf(8,0)n1=24
n2=16
hcf(24,16)
hcf(16,8)
hcf(8,0)
STACK
Representation of stack operation

8. Heap
• The heap is an area of memory reserved for dynamic
memory allocation.
• Dynamic allocation is a technique in which a program
can acquire storage space in main memory.
• In this method , the space for the program is allocated
from the free space during execution of the program.
• This free space is called Heap

9. Memory allocation functions
1. malloc()
This function is used to allocate memory space in
bytes to the variable of different data types.
Example: ptr = (int*)malloc(20);
Ptr=(data type*)malloc(given size);

10. #include<stdio.h>
#include<stdlib.h>
main()
{
int k,*p,j=0,sum=0;
printf("How many numbers:");
scanf("%d",&k);
p=(int*)malloc(k*sizeof(int));
printf("n enter the numbers");
while(j!=k)
{
scanf("%d", p+j);
j++;
}
j=0;
printf("sum: ");
while(j!=k)
{
sum=sum+*(p+j);
j++;
}
printf("%d",sum);
}
How many numbers:3
enter the numbers: 1 2 3
Sum: 6

11. 2. calloc()
• This function is useful for allocating multiple blocks
of memory . It is declared with two arguments.
• It allocate 4 blocks of memory and each block
contain 2 bytes
• This function is usually used for allocating memory
for array and structure
Ptr =(int*)calloc(4,2);

12. #include<stdio.h>
#include<stdlib.h>
main()
{
int k,*p,j=0,sum=0;
printf("How many numbers:");
scanf("%d",&k);
p=(int*)calloc(k,2);
printf("nenter the numbers");
while(j!=k)
{
scanf("%d",p+j);
j++;
}
j=0;
printf("sum: ");
while(j!=k)
{
sum=sum+*(p+j);
j++;
}
printf("%d",sum);
}
How many numbers:3
enter the numbers: 1 2 3
Sum: 6

13. 3.free()
• This function is used to release the memory allocated
by memory allocating functions.
• ptr is the pointer and free() releases the memory
occupied by the pointer variable.
free(ptr);

14. 4.realloc()
• This function reallocate the main memory.
• This are made to shrink or enlarge the previously
allocated memory.
• It returns the address of the reallocated block.
• If the block cannot be reallocated returns NULL

15. #include<stdio.h>
#include<stdlib.h>
main()
{
char *str;
str=(char*)malloc(6);
str=("india");
printf("str=%s",str);
str=(char*)realloc(str,10);
str=("hindustan");
printf("nnew str=%s",str);
free(str);
}
str=india
new str=hindustan

16. Stack vs Heap
stack
• local variables only.
• limit on stack size.
• variables cannot be resized.
• space is managed efficiently
by CPU, memory will not
become fragmented .
heap
• variables can be accessed
globally .
• no limit on memory size.
• variables can be resized
using realloc() .
• no guarantee on efficient use
of space.

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