Operands for sizeof operator

The sizeof operator is used to return the size of its operand, in bytes. This operator always precedes its operand. The operand either may be a data-type or an expression. Let’s look at both the operands through proper examples.

1. type-name: The type-name must be specified in parentheses.

   sizeof(type - name)

   Let’s look at the code:
   

   C

   #include <stdio.h>
   int main()
   {
       printf("%lu\n", sizeof(char));
       printf("%lu\n", sizeof(int));
       printf("%lu\n", sizeof(float));
       printf("%lu", sizeof(double));
       return 0;
   }

   C++

   #include <iostream>
   using namespace std;
   
   int main()
   {
       cout << sizeof(char)<<"\n";
       cout << sizeof(int)<<"\n";
       cout << sizeof(float)<<"\n";
       cout << sizeof(double)<<"\n";
       return 0;
   }
   Output:

   1
   4
   4
   8
   

2. expression: The expression can be specified with or without the parentheses.

   // First type
   sizeof expression
   
   // Second type
   sizeof(expression)

   The expression is used only for getting the type of operand and not evaluation. For example, below code prints value of i as 5 and the size of i a
   

   C

   #include <stdio.h>
   
   int main()
   {
       int i = 5;
       int int_size = sizeof(i++);
   
       // Displaying the size of the operand
       printf("\n size of i = %d", int_size);
   
       // Displaying the value of the operand
       printf("\n Value of i = %d", i);
   
       getchar();
       return 0;
   }

   C++

   #include <iostream>
   using namespace std;
   
   int main()
   {
       int i = 5;
       int int_size = sizeof(i++);
   
       // Displaying the size of the operand
       cout << "\n size of i = " << int_size;
   
       // Displaying the value of the operand
       cout << "\n Value of i = " << i;
   
       return 0;
   }
   
   // This code is contributed by SHUBHAMSINGH10
   Output:

   size of i = 4
    Value of i = 5
   

References:
http://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#The-sizeof-Operator