Declaring a pointer
Like variables, pointers have to be declared before they can be used in your program. Pointers can be named anything you want as long as they obey C's naming rules. A pointer declaration has the following form.
data_type * pointer_variable_name;
Here,
Let's see some valid pointer declarations
int *ptr_thing; /* pointer to an integer */
int *ptr1,thing;/* ptr1 is a pointer to type integer and thing is an integer variable */
double *ptr2; /* pointer to a double */
float *ptr3; /* pointer to a float */
char *ch1 ; /* pointer to a character */
float *ptr, variable;/*ptr is a pointer to type float and variable is an ordinary float variable */
Initialize a pointer
After declaring a pointer, we initialize it like standard variables with a variable address. If pointers are not uninitialized and used in the program, the results are unpredictable and potentially disastrous.
To get the address of a variable, we use the ampersand (&)operator, placed before the name of a variable whose address we need. Pointer initialization is done with the following syntax.
pointer = &variable;
A simple program for pointer illustration is given below:
#include <stdio.h>
int main()
{
int a=10; //variable declaration
int *p; //pointer variable declaration
p=&a; //store address of variable a in pointer p
printf("Address stored in a variable p is:%x\n",p); //accessing the address
printf("Value stored in a variable p is:%d\n",*p); //accessing the value
return 0;
}
Output:
Address stored in a variable p is:60ff08
Value stored in a variable p is:10
Operator |
Meaning |
* |
Serves 2 purpose
|
& |
Serves only 1 purpose
|