Struct as a data container and Marshal
- Book: title, author
- Order: book, reader, date
- Reader: name, email, city, street, house
- Author: name, biography
- Library: books, orders, readers, authors
- Who often takes the book
- What is the most popular book
- How many people ordered one of the three most popular books
- Save all Library data to file(s)
- Get all Library data from file(s)
p.s. in "How many people ordered one of the three most popular books" it was displayed three most popular books and the number of people who ordered those(three) books For example, the most pop.book is "The Art Of Happiness" was ordered 6 times