Pointers in C

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Pointers :- it is used to access the memory locations and manipulating the address of the variables. Pointer is only thing that creates the big difference between C and the famous language Java , .net .
we use pointers for accessing the memory location.

Operator:-  & called  "ampersand"  or "address of"  , declaring any variable with &  represents address or memory location.

EX:-
main()
{
int a=10;
printf("%d",a);       //print the value of a
printf("%u",&a);    //prints the address of a
}

OUTPUT:-   10  -value
                     268772 -memory address

it simply means "10" store at "268772" memory location named "a". "a" is the name of memory address.


Declaration of Pointer:- * is used for declaring pointer type variable. and if a variable is pointer type and we write *variable name then it directly represents the value at variable name.
mainly it refers the value present at that memory  location.

int *p;  // int type pointer
char *c;  //char type pointer

Simple Program for Pointers:-

main()
{
int a=10;
int *b;
b=&a;
printf("%d",a);
printf("%u",&a);
printf("%x",b);
printf("%x",*b);
}

output:- 10
             268772
              268772
               10

Description:-  * is used for declaring pointer type variables.
first it simply prints the value of "a"
&a   prints the address of the a or memory location.
b =&a   b is a pointer type variable in which we store the address of a. so on printing b it prints the address of a.
*b  it refers to the value at b .simply it prints the value present at that memory locations.

We can also apply arithmetic operations on the pointer like increment \decrement operator,

Ex:-
int *a,*b;
++a;
--a;
a==b;

this simply increment or decrement the address not the values.

Pointers with Arrays:- We can also print the address of the elements of the array by using the pointer.

Ex:-
main()
{
int a[3];
for(int i=0;i<3;i++)
printf("%x",&a[i]);
}

output:-it prints the address. of all 3 elements.


Pointers with Functions:- it is also known as call by reference.passing the address as a argument of the function.

Ex:-
void swap(int *a , int *b);
main()
{
int a=1,b=2;
printf("%d%d",a,b);
swap(&a,&b);
printf("%d%d",a,b);
}
void swap(int *a, int *b)
{
int c;
c=*a;
*a=*b;
*b=c;
}
output:-
1 2
2 1

Description:-in function declaration we define pointer type variable.
in function calling we pass the address of the variable.
 in function definition it takes the value at that address .
simply we transfer the value through their address.
so by this way we can use pointer into the function.

we discuss all the examples on pointers in example section.