static array of structs clarification questions

[WhatMeWorry via Digitalmars-d-learn]

I was thinking about fixed length arrays of structures the other 
day so I played around with the flowing code:

   struct Foo
    {
        int    i;
        string str;
        void info() { writeln("i = ", i, "str = ", str); }
    }
    Foo[2] foos;

    auto f1 = Foo(1, "6chars");  // this string is 6 chars long
    auto f2 = Foo(2, "ThisVeryVeryVeryLongStringHas36Chars");

    foos[0] = f1;
    foos[1] = f2;

    writeln("f1 = ", foos[0]);
    writeln("f2 = ", foos[1]);

    writeln("array foos size in bytes is ", foos.arrayByteSize);
    writeln("array foos has ", foos.length, " elements");
    writeln("foos array consists of ", foos);

The output was
f1 = Foo(1, "6chars", null)
f2 = Foo(2, "ThisVeryVeryVeryLongStringHas36Chars", null)
array foos size in bytes is 32
array foos has 2 elements
foos array consists of [Foo(1, "6chars", null), Foo(2, 
"ThisVeryVeryVeryLongStri
ngHas36Chars", null)]


question #1: The static array must contain the fat pointers to 
str variables. But where is the string data itself actually held: 
the stack? the heap? somewhere else? (does it vary depending on 
location or scope)

question #2: If the above struct was to contain the same struct 
and the second one contains a third, how would the lower structs 
be allocated?  Is it "turtles all the way down?

question #2: Of what use is the nulls in the array elements?  
When I took out the member function: void info(), the nulls went 
away.

Thanks.