Pointer in C Language

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Pointer in C Language

Pointer is one of an important feature of c language. This is the most powerful feature of c language. Pointer is a variable same as other variable but with a little different. The variable we declared except pointer variable holds the value, but a pointer variable holds the address of a variable of same pointer declaration type.

The declaration of a pointer type variable

int*p;

The declaration tells -  p is a pointer variable of integer type which holds only the address of an integer type variable.

Like this the declaration of a character, float type variable is

char*p;

float*p;

Let us see with this example

The declaration of a simple integer type variable is

int var = 233;

           Var

233

  

        1635

When the control execute this statement, it allocates 2 bytes of memory for this variable let the address of the first byte is 1635and stores integer constant 233 in this 2 bytes of memory and name the location of the memory as var. When we are going to access the value of the variable there is no use of the address of the variable. The simple variable may be a signed variable or may be an unsigned variable.

int * p;

int var=233;

p=&var;

        var

233

  

        1635

            p

1635

  

        3856

When the control execute, it allocates 2 bytes of memory for pointer variable let the address 3856 and 2 bytes of memory for  general variable let the address 1635 and stores integer constant 233 in this 2 bytes of memory and stores the address of the general variable 1635 in the pointer variable. The pointer variable always stores unsigned integer type value because the address of any variable is unsigned integer type..

Let us see an example

main()

{

  int * p;

  int var=233;

  p=&var; // assigning address to the pointer

  printf("%d",var);

  printf("%u",p);

  printf("%d",*p);

}

 The output is 233 1635 233

When we are accessing a pointer variable like any other normal variable  like in second printf statement it gives the value stored in the variable p i.e 1635. If we want to access the value stored at the memory location 1635 then we have to use *p not only p like in third printf.

How to read a pointer variable

    1. int *p;

            This can be read as - p is a pointer variable which can hold the address of an integer variable.

    2. char *p;

            This can be read as - p is a pointer variable which can hold the address of a character variable.

    3. float *p;

        This can be read as - p is a pointer variable which can hold the address of a float variable.

    4. double *p;

        This can be read as - p is a pointer variable which can hold the address of a double variable.

    5. int**p;

        This can be read as - p is a pointer variable which can hold the address of another pointer variable which hold the address of an integer variable

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