/*
 This is an example of the MONOLITHIC STYLE of design.
 Several features are to be noted:
 (a) Physical modules:  1 file
 (b) Logical  modules:  8 functions
 (c) Language supported data abstractions used: file.
 (d) Application defined data abstractions: Vector.
 (e) Data encapsulation used: NO
     The type Vector is not encapsulated in its own
     physical module (file).
 (f) Information hiding used: Limited
     In reference to type Vector we note the following:
     - The representation of the type is completely visible 
       and accessable to the client code, main().
     - The client explicitly references and accesses the
       internal components of type Vector (x,y) in the i/o
       statements that read and write Vectors.
     - Limited information hiding is demonstrated in that
       the internal view of Vectors as "cartesian" or "polar"
       is hidden in the functions that manipulate Vectors.
       The internal view is not revealed in the client code
       either; even though the client reads and writes the
       components x,y of Vectors, there is nothing in the
       client that assumes or exploits one particular view
       over the other. However, there is nothing to prevent
       the client from exploiting the fact that the internal
       view of Vectors is Cartesian - we have a well-written
       client.
 (g) Decomposition stype:     FUNCTIONAL
 (h) Degree of OO'ness:       
     - Variables are used to denote File objects. The C language
     provides various library functions (methods) for manipulating
     file objects. Furthermore, the internal representation of
     file objects is effectively hidden from all client code.
     The fopen() function is effectively a constructor for file
     objects.
     - Within a single instance of a "problem," Vector variables
     are used consistent with an object view; that is, variables
     always denote the same Vector instance - this is a virtue 
     of the client code, not a virtue of the C language.
     Operations on Vectors are consistent with an object view.
42   */