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Pointers & References

Pointers store address of variables or a memory location.

// General syntax
datatype *var_name; 

// An example pointer "ptr" that holds
// address of an integer variable or holds
// address of a memory whose value(s) can
// be accessed as integer values through "ptr"
int *ptr;  

Using a Pointer:

To use pointers in C, we must understand below two operators.

  • 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.
// The output of this program can be different 
// in different runs. Note that the program 
// prints address of a variable and a variable 
// can be assigned different address in different 
// runs. 
#include <stdio.h> 

int main() 
// Prints address of x 
printf("%p", &x); 

return 0; 
  • 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 be a * before its name.
// C program to demonstrate declaration of 
// pointer variables. 
#include <stdio.h> 
int main() 
    int x = 10; 
// 1) Since there is * in declaration, ptr 
// becomes a pointer varaible (a variable 
// that stores address of another variable) 
// 2) Since there is int before *, ptr is 
// pointer to an integer type variable 
int *ptr; 

// & operator before x is used to get address 
// of x. The address of x is assigned to ptr. 
ptr = &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. This is also called Dereferencing.


My name is Truong Thanh, graduated Master of Information Technology and Artificial Intelligent in Frankfurt University,Germany. I create this Blog to share my experience about life, study, travel...with friend who have the same hobbies.

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