title: Can array and nullable types be used before they are declared?
body: <p>I quote the following paragraphs from the book: 
  <strong>The C# Programming Language
  Fourth Edition</strong> </p>
  
  <blockquote>
    <p>C# supports single- and
    multi-dimensional arrays of any type.
    Unlike the types listed above, array
    types do not have to be declared
    before they can be used. Instead,
    array types are constructed by
    following a type name with square
    brackets. For example, int[] is a
    single-dimensional array of int,
    int[,] is a two-dimensional array of
    int, and int[][] is a
    single-dimensional array of
    single-dimensional arrays of int.</p>
  </blockquote>
  
  <p>and</p>
  
  <blockquote>
    <p>Nullable types also do not have to be
    declared before they can be used. For
    each non-n ullable value type T there
    is a corresponding nullable type T?,
    which can hold an additional value
    null. For instance, int? is a type
    that can hold any 32 bit integer or
    the value null.</p>
  </blockquote>
  
  <p>How to use array and nullable types without declaring them in advance?</p>