Describe the role of envelope and letter classes.

I was actually asked this question at one of my interviews. I guess the single purpose of this question is to paralyze the interviewee. In my case the interviewer has achieved the goal and I am glad I did not pass an interview to that company. The interviewer actually tried to fetch a basic overview of C++ paradigms and design patterns (this envelope/letter paradigm is described in the book of Coplien from 1995) While I do not question the importance of design patterns, all I was talking to agreed that in this form the question demonstrate inability of the interviewer to conduct the interview. You may safely ignore this question if you asked :)