C Programming language

# Pointer

In c a pointer is a variable that points to or references a memory location in which data is stored. Each memory cell in the computer has an address that can be used to access that location so a pointer variable points to a memory location we can access and change the contents of this memory location via the pointer.

Pointer is a address variable that hold the address of another variable. We can have a pointer to any variable type. The & is a unary operator that gives the address of a variable. The * (indirection or dereference operator), that gives the contents of an object that pointed to by a pointer.

(&) Ampersand operator

//Using & operator show the address of variable

void main( )
{
	int a = 5 ;
	printf ( "\nAddress of a = %u", &a );
	printf ( "\nValue of a = %d", a );
}

Note: In above example variable a memory address is 1444. Means using this & we find the memory address.

Syntax

data_type_name *variable_name  

int *ptr; //Declare a pointer

# Now using pointer, once we declare a pointer variable we must point it to something we can do this by assigning to the pointer the address of the variable like:

To access memory address of variable x you have to use pointer. To declare pointer you use asterisk notation (*) after pointer's data type and before pointer name as follows:

int x = 10;

/* Now  pointer ptr to points to memory address of variable x */
const int *ptr;

/* you can use address-of operator (&) */
ptr = &x;

/* Show address of variable x */
printf("Address of x is %d\n", ptr); 

/* Variable x */
printf("Value of x is %d\n", *ptr); 

/* you can change the content of variable x 
using poiter variable */

*ptr += 10;// Increasing the value
printf("Value of x after increasing %d\n",x);

*ptr -= 5;// Decreasing the value
printf("Value of x after decreasing %d\n",x);