What is the difference between checked and unchecked?

Question

What is the difference between

checked(a + b)

and

unchecked(a + b)

?

Answer 1

The Language Specification has a good article on the differences.

The checked and unchecked operators are used to control the overflow checking context for integral-type arithmetic operations and conversions.

class Test
{
   static readonly int x = 1000000;
   static readonly int y = 1000000;
   static int F() {
      return checked(x * y);      // Throws OverflowException
   }
   static int G() {
      return unchecked(x * y);   // Returns -727379968
   }
   static int H() {
      return x * y;               // Depends on default
   }
}