Pointers in C and C++

Pointers in C and C++

A pointer is a variable that stores the address of another variable. Unlike other variables that hold values of a certain type, pointer holds the address of a variable. For example, an integer variable holds (or you can say stores)
an integer value, however an integer pointer holds the address of a integer variable.
 Pointers store address of variables or a memory location.
 
Syntax:

datatype *var_name;
Ex: int *ptr; 
 
To access address of a variable to a pointer, we use the unary operator & (ampersand) that returns the address of that variable. For example &x gives us address of variable x.

#include <stdio.h>
 
int main()
{
    int x;
 
    // Prints address of x
    printf("%p", &x);
 
    return 0;
}
EX:
#include <stdio.h>
int main()
{
   int num = 10;
   printf("Value of variable num is: %d", num);
   /* To print the address of a variable we use %p
    * format specifier and ampersand (&) sign just
    * before the variable name like &num.
    */
   printf("\nAddress of variable num is: %p", &num);
   return 0;
}

Output:

Value of variable num is: 10
Address of variable num is: 0x7fff5694dc58


One more operator is unary * (Asterisk) which is used for two things :
To declare a pointer variable: When a pointer variable is declared in C/C++, there must a * before its name.

 

C program for pointer variables.

#include <stdio.h>
int main()
{
    int x = 10;
    int *ptr;        //ptr is an integer type pointer variable
    ptr = &x;        //& used for get address so ptr store the address of x 
    return 0;
}

To access the value stored in the address we use the unary operator (*) that returns the value of the variable
located at the address specified by its operand.

 C program  of * for pointers in C
#include <stdio.h>
 
int main()
{
    int y = 5;
    int *ptr = &y;
    printf("Value of y = %d\n", *ptr);
    printf("Address of y = %p\n", ptr);
   *ptr = 10;
    printf("After doing *ptr = 10, *ptr is %d\n", *ptr);
    return 0;
}