C++ Tutorial/Operators statements/sizeof

Demonstrate sizeof.

<source lang="cpp">#include <iostream> using namespace std;

int main() {

 char ch; 
 int i; 

 cout << sizeof ch << " "; // size of char 
 cout << sizeof i << " ";  // size of int 
 cout << sizeof (float) << " "; // size of float 
 cout << sizeof (double) << " "; // size of double 

 return 0; 

}</source>

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Object sizes

<source lang="cpp">#include <iostream> using std::cout; using std::endl; class Box {

 public:
   Box() :length(1.0), width(1.0), height(1.0), pMaterial("new") {}
   
   int totalSize() {
     return sizeof(length) + sizeof(width) + sizeof(height) + sizeof(pMaterial

);

   }
 private:
   char* pMaterial;
   double length;
   double width;
   double height;

}; int main() {

 Box box;
 Box boxes[10];
 cout << endl            << "The data members of a Box object occupy "
      << box.totalSize() << " bytes.";
 cout << endl           << "A single Box object occupies "
      << sizeof (Box) << " bytes.";
 cout << endl           << "An array of 10 Box objects occupies "
      << sizeof(boxes)  << " bytes."
      << endl;
 return 0;

}</source>

The data members of a Box object occupy 28 bytes.
A single Box object occupies 32 bytes.
An array of 10 Box objects occupies 320 bytes.

sizeof a class

<source lang="cpp">/* The following code example is taken from the book

* "C++ Templates - The Complete Guide"
* by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
*
* (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <iostream>

class EmptyClass { }; int main() {

   std::cout << "sizeof(EmptyClass): " << sizeof(EmptyClass)
             << "\n";

}</source>

sizeof(EmptyClass): 1

sizeof a union

<source lang="cpp">#include<iostream.h> union u_tag{

  int i;
  double d;

}u={88}; struct s_tag{

   int i;
      double d;

}s={66,1.234}; int main() {

   int size;
      size=sizeof(union u_tag);
   cout<<"sizeof(union u_tag)="<<size<<endl;
   u.i=100;
      cout<<"u.i="<<u.i<<endl;
      u.d=1.2345;
      cout<<"u.d="<<u.d<<endl;
      size=sizeof(u.d);
      cout<<"sizeof(u.d)="<<size<<endl;
      cout<<"s.i="<<s.i<<endl;
      cout<<"s.d="<<s.d<<endl;
      size=sizeof(struct s_tag);
      cout<<"sizeof(struct s_tag)="<<size<<endl;

}</source>

sizeof(union u_tag)=8
u.i=100
u.d=1.2345
sizeof(u.d)=8
s.i=66
s.d=1.234
sizeof(struct s_tag)=16

Use sizeof operator on an array name: returns the number of bytes in the array

<source lang="cpp">#include <iostream> using std::cout; using std::endl; int main() {

  double array[ 20 ];
  cout << "The number of bytes in the array is " << sizeof( array );
  return 0;

}</source>

The number of bytes in the array is 160

Using the sizeof operator for base class and derived class

<source lang="cpp">#include <iostream>

1. include <ostream>

class base {}; class derived : public base {}; int main() {

 using namespace std;
 cout << sizeof(base)  << "\n";      
 cout << sizeof(derived)  << "\n";   
 base b[3];
 
 cout << sizeof(b) << "\n";          
 derived d[5];
 cout << sizeof(d) << "\n";          

}</source>

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