Use sizeof operator on an array name: returns the number of bytes in the array : sizeof « Operators statements « C++ Tutorial

1. C++ Tutorial
2. Operators statements
3. sizeof

#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;
}

The number of bytes in the array is 160