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Pointer In C Language

          Introduction To Pointer:
About Pointer:-
*POINTER is a variable whose value is the address of another variable
*Every variable is a memory location and every memory location
 has its address defined which can be accessed using ampersand(&)
 operator,which denotes an address in memory
*Dynamic memory allocation,cannot be performed without using pointers.
Let's start learning them in simple and easy steps.
pointer variable declaration:-
data_type *variable_name;
*The asterisk (*) used to declare a pointer is the same asterisk used for
  multiplication.
some of the valid pointer declarations:-
int *in;            //pointer to an integer 
double *db;  // pointer to a double 
float *fl;        // pointer to a float 
char *chr    //pointer to a character 
*The only difference between pointers of different data types
is the data type of the variable or constant that the pointer points to.
Implementation Of Pointers:-
This is devided into 3 steps:-
1)define a pointer variable,
2)assign the address of a variable to a pointer
3)access the value at the address available in the pointer variable by using 
unary operator*Which returns the value of the variable located at the address
Example Program:-
#include <stdio.h>
int main ()
{
int a = 20; // actual variable declaration 
int *i;     // pointer variable declaration 
i = &a;    // store address of var in pointer variable
printf("Address of a variable= %x\n", &a);
/* address stored in pointer variable */
printf("Address stored in i variable: %x\n", ip );
//access the value using the pointer
printf("Value of *i variable= %d\n", *i );
return 0;
}
The Output Of This Program Will Be:-
Address of a variable= d2051594
Address stored in i variable: d2051594
Value of *i variable= 50
A Null Pointer:-
*A pointer that is assigned NULL is called a null pointer.
*The NULL pointer is a constant with a value of zero.
*It Is defined in several standard libraries.
Example Program:-
In This Example We Will Check The Value Of Null Pointer.
#include <stdio.h>
int main ()
{
int *ptr = NULL; //null pointer declration
printf("The value of Null ptr is = %x\n", ptr);
return 0;
}
The OutPut Of Given Program Is:-
The value of Null ptr is = 0
                 
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