As a part of my consisting cleaning up project, I set up a large CD shelf in my house and arranged all my CDs on it. It wasn't an easy job because the number of my CDs comes up to more than one thousand. It's quite a doddle for computers to sort one thousand of data and whatever sorting algorithm works, but for me as a human, it took whole day and it was a very important problem how to sort them. My first process was to group all my CDs by its size. As you know, there are two size of CD; 12 cm and 8 cm. It took more than one hour to make two piles of CDs. The second process was to divide each pile into five classes: classical, jazz, pop & rock, Japanese pop & rock and others. It was a two hour job, but the process was the hardest. I had to sort each class of CDs by its artist's name and title. It took more than five hours and I was very tired when I finished all the work. However, I am satisfied with the result. I can now pick up any CD I want in a second. All I have to do next is to store all of my favorite CDs into iTunes library and sell out the disused ones to the second hand CD shop. I think it's not the age of storing CDs on the shelf.