Difference between revisions of "Interview Preparation Pointers"

Revision as of 15:02, 17 December 2016

Pointers : A pointer is a variable who's value is address of some other variable i.e. it can be address of some memory location.

<varaible_type> *<name>
eg : 
     int *pointer_to_integer

The above example , we have declared a pointer to a variable (pointer_to_integer), the variable stores the address of an integer .

Implementation of Pointer :

Code:

#include <stdio.h>
int main(void) {
	int var = 20;
	int *p;
	p = &var;
	
	printf("Pointer %d\n",var);
	printf("Pointer %d\n",&var);     // Prints the address of the varaible (var)
	printf("Pointer %d\n",p);        
	printf("Pointer %d\n",*p);	     // Prints the value that (p) points to   
	return 0;
}

Output :

Pointer 20
Pointer 1809844068
Pointer 1809844068
Pointer 20

Malloc

  The Malloc function dynamically allocates memory when required. The function allocates size of byte of memory and returns a pointer to the first byte of NULL.

Syntax:
pointer = (type)malloc(size in bytes);
 
Code:

int* p;                        //Declare pointer                          
p = (int*)malloc(sizeof(int)); // Pointer equal to pointer type int that contain memory address space of int
*p = 5;                        // Finally pointer points to location containing value 5