Where are the main data types usually stored in the system?

In C#, main data types (e.g., int, double, bool) are value types and are usually stored on the stack when declared locally within methods.

If such types are declared as class fields, they are stored on the heap along with the object.

Example:

void Method()
{
    int x = 10; // stored on the stack
}

class MyClass
{
    int y; // stored on the heap along with the object
}

Thus, the location of main data types depends on the context of their use: local variables — on the stack, object fields — on the heap.