Double Pointer

In C, a double pointer is a pointer that holds the memory address of another pointer. It allows indirect access to the value of a variable.

Syntax

A double pointer is declared using two asterisks (**) before the pointer variable name:

type **name

• type: The type of data the double pointer will point to (e.g., int, char, etc.).
• name: The identifier for the double pointer.

Example

The following example demonstrates how a double pointer is declared and used:

# include <stdio.h>

int main() {
  int value = 35;
  int *pointer = &value; // Pointer to an integer (stores the address of 'value')
  int **doublePointer = &pointer; // Double pointer to an integer pointer (stores the address of 'pointer')

  // Printing the values
  printf("Value of value: %d\n", value); // Direct access to value
  printf("Value of *pointer: %d\n", *pointer); // Dereferencing pointer to access value
  printf("Value of **doublePointer: %d\n", **doublePointer); // Dereferencing double pointer twice to access value

  // Printing the addresses
  printf("Address of value: %p\n", (void*)&value); // Address of the variable 'value'
  printf("Address of pointer: %p\n", (void*)&pointer); // Address of the pointer 'pointer'
  printf("Address of doublePointer: %p\n", (void*)&doublePointer); // Address of the double pointer 'doublePointer'

  return 0;
}

The above code will give the following output:

Value of value: 35
Value of *pointer: 35
Value of **doublePointer: 35
Address of value: 0x7ffcbffdcc14
Address of pointer: 0x7ffcbffdcc18
Address of doublePointer: 0x7ffcbffdcc20

In the example:

• value is an integer variable.
• pointer is a pointer tha stores the address of value.
• doublePointer is a double pointer that stores the address of the pointer.