POINTERS, DECLARATION, INITILIZATION

POINTERS

            A pointer is a variable which holds the memory address of another variable. 

Pointer Declaration:              As similar to an ordinary variable, pointer variables must be declared before they are using.  A pointer variable is declared by preceding its name with an asterisk * symbol.  The symbol indicates that the variable is a pointer variable.  The general format of declaring a pointer variable is:

            Syntax:           datatype *ptrvariable;

Where,

Ø  ptrvariable is name of the pointer variable that follows same rules as a valid identifier.

Ø  ‘*’ tells the compiler that ptrvariable is a pointer variable.

Ø  datatype is the type of the data that the pointer is allowed to hold the address.

Example:        int *ptr1;

Here,   ptr1 is a pointer variable that can points to an integer type variable.

Example:        float *ptr2;

Here,   ptr2 is a pointer variable that can points to a float type variable.

            Example:        char *ptr3;

Here,   ptr3 is a pointer variable that can points to a character type variable.

Example:         int *ptr1;                     float *ptr2;                  char *ptr3;

                        2 bytes                         2 bytes                         2 bytes

                           ptr1                              ptr2                               ptr3

Note:   Any type of pointer occupies only 2 bytes of memory.  Since, pointer holds address of the variable which is always an unsigned integer.

Initializing Pointers:              Once a pointer variable has been declared, it can be initialized using an assignment operator as:

            Syntax:           ptrvariable = &ordinaryvariable;

           

Example:        ptr = &x;

Where, x is an ordinary variable.

Here, address of the variable x is stored in ptr.  With this, a link is formed from pointer variable to ordinary variable.

            Example:         int x,*ptr;

                                    x=10;

                                    ptr=&x;

           

A pointer variable can also be initialized at the time of its declaration itself.

                        Example:        int x, *ptr = &x;