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 The sizeof Operator


Get the Memory Size

We introduced in the data types chapter that the memory size of a variable varies depending on the type:

Data Type Size
int 2 or 4 bytes
float 4 bytes
double 8 bytes
char 1 byte

The memory size refers to how much space a type occupies in the computer's memory.

To actually get the size (in bytes) of a data type or variable, use the sizeof operator:

Example

int myInt;
float myFloat;
double myDouble;
char myChar;

printf("%lu\n", sizeof(myInt));
printf("%lu\n", sizeof(myFloat));
printf("%lu\n", sizeof(myDouble));
printf("%lu\n", sizeof(myChar));
Try it Yourself »

Note that we use the %lu format specifer to print the result, instead of %d. It is because the compiler expects the sizeof operator to return a long unsigned int (%lu), instead of int (%d). On some computers it might work with %d, but it is safer to use %lu.

Why Should I Know the Size of Data Types?

Knowing the size of different data types is important because it says something about memory usage and performance.

For example, the size of a char type is 1 byte. Which means if you have an array of 1000 char values, it will occupy 1000 bytes (1 KB) of memory.

Using the right data type for the right purpose will save memory and improve the performance of your program.

You will learn more about the sizeof operator later in this tutorial, and how to use it in different scenarios.


×

Contact Sales

If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail:
sales@w3schools.com

Report Error

If you want to report an error, or if you want to make a suggestion, send us an e-mail:
help@w3schools.com

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.