C++ sizeof Operator (original) (raw)

Last Updated : 09 Dec, 2024

The **sizeof operator is a unary compile-time operator used to determine the size of variables, data types, and constants in bytes at compile time. It can also determine the size of classes, structures, and unions.

Let's take a look at an example:

C++ `

#include using namespace std;

int main() {

cout << sizeof(int);

return 0;

}

`

**Explanation: The above code outputs the size of the integer data type for the compiler on which the program is executed. Here, it is 4 bytes.

This article covers the syntax, usage, and common examples of sizeof operator in C++:

Table of Content

• Syntax of sizeof in C++
• Examples of sizeof in C++
  • Find Size of Different Primitive Data Types
  • Find the Size of Different Variables
  • Find the Size of an Array Using sizeof
  • Find the Size of Class

**Syntax of sizeof in C++

The sizeof operator can be used to find the size of a type or a variable in C++ as shown:

**sizeof (type)
**sizeof (expression)

Examples of sizeof in C++

The below examples demonstrate the common usage of sizeof in C++:

Find Size of Different Primitive Data Types

C++ `

#include <bits/stdc++.h> using namespace std;

int main() {

// Finding the size of different data types
cout << "Size of char: " << sizeof(char) << endl;
cout << "Size of int: " << sizeof(int) << endl;
cout << "Size of float: " << sizeof(float) << endl;
cout << "Size of double: " << sizeof(double) << endl;
cout << "Size of long: " << sizeof(long);

return 0;

}

`

Output

Size of char: 1 Size of int: 4 Size of float: 4 Size of double: 8 Size of long: 8

Find the Size of Different Variables

C++ `

#include <bits/stdc++.h> using namespace std;

int main() { int a; float b; char g;

// Printing size of all three variables
cout << "Size of a:  " << sizeof(a) << endl;
cout << "Size of b:  " << sizeof(b) << endl;
cout << "Size of g:  " << sizeof(g);

return 0;

}

`

Output

Size of a: 4 Size of b: 4 Size of g: 1

**Find the Size of an Array Using sizeof

C++ `

#include <bits/stdc++.h> using namespace std;

int main() { int arr[] = {1, 2, 3, 5, 6};

  // Finding the length of array
  int n = sizeof(arr) / sizeof(arr[0]);

  cout << n;
  return 0;

}

`

Find the Size of Class

C++ `

#include <bits/stdc++.h> using namespace std;

class A { int x; A(int val = 10) : x(val){} };

int main() {

  // Finding size of class A (size of the objects
  // of class A)
cout << "Size of Class a: " << sizeof(A);
return 0;

}

`