Menu
×
   ❮   
HTML CSS JAVASCRIPT SQL PYTHON JAVA PHP HOW TO W3.CSS C C++ C# BOOTSTRAP REACT MYSQL JQUERY EXCEL XML DJANGO NUMPY PANDAS NODEJS R TYPESCRIPT ANGULAR GIT POSTGRESQL MONGODB ASP AI GO KOTLIN SASS VUE DSA GEN AI SCIPY AWS CYBERSECURITY DATA SCIENCE
     ❯   

C Pointers


Creating Pointers

You learned from the previous chapter, that we can get the memory address of a variable with the reference operator &:

Example

int myAge = 43; // an int variable

printf("%d", myAge);  // Outputs the value of myAge (43)
printf("%p", &myAge); // Outputs the memory address of myAge (0x7ffe5367e044)
Try it Yourself »

A pointer is a variable that stores the memory address of another variable as its value.

A pointer variable points to a data type (like int) of the same type, and is created with the * operator.

The address of the variable you are working with is assigned to the pointer:

Example

int myAge = 43;     // An int variable
int* ptr = &myAge;  // A pointer variable, with the name ptr, that stores the address of myAge

// Output the value of myAge (43)
printf("%d\n", myAge);

// Output the memory address of myAge (0x7ffe5367e044)
printf("%p\n", &myAge);

// Output the memory address of myAge with the pointer (0x7ffe5367e044)
printf("%p\n", ptr);
Try it Yourself »

Example explained

Create a pointer variable with the name ptr, that points to an int variable (myAge). Note that the type of the pointer has to match the type of the variable you're working with (int in our example).

Use the & operator to store the memory address of the myAge variable, and assign it to the pointer.

Now, ptr holds the value of myAge's memory address.


Dereference

In the example above, we used the pointer variable to get the memory address of a variable (used together with the & reference operator).

You can also get the value of the variable the pointer points to, by using the * operator (the dereference operator):

Example

int myAge = 43;     // Variable declaration
int* ptr = &myAge;  // Pointer declaration

// Reference: Output the memory address of myAge with the pointer (0x7ffe5367e044)
printf("%p\n", ptr);

// Dereference: Output the value of myAge with the pointer (43)
printf("%d\n", *ptr);
Try it Yourself »

Note that the * sign can be confusing here, as it does two different things in our code:

  • When used in declaration (int* ptr), it creates a pointer variable.
  • When not used in declaration, it act as a dereference operator.

Good To Know: There are two ways to declare pointer variables in C:

int* myNum;
int *myNum;

Notes on Pointers

Pointers are one of the things that make C stand out from other programming languages, like Python and Java.

They are important in C, because they allow us to manipulate the data in the computer's memory. This can reduce the code and improve the performance. If you are familiar with data structures like lists, trees and graphs, you should know that pointers are especially useful for implementing those. And sometimes you even have to use pointers, for example when working with files and memory management.

But be careful; pointers must be handled with care, since it is possible to damage data stored in other memory addresses.




×

Contact Sales

If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail:
[email protected]

Report Error

If you want to report an error, or if you want to make a suggestion, send us an e-mail:
[email protected]

W3Schools is optimized for learning and training. Examples might be simplified to improve reading and learning. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using W3Schools, you agree to have read and accepted our terms of use, cookie and privacy policy.

Copyright 1999-2024 by Refsnes Data. All Rights Reserved. W3Schools is Powered by W3.CSS.