You are currently reading the main folder of the material for the master lecture on object-oriented design given at Central school in the Data science Master. The audience is - either students with no prior Java exposure and/or limited OOP exposure - students that followed a lecture on Java. In any case we do not expect students to know any specific Java knowledge. This lectures is NOT about Java but about object-oriented design. So the lecture has been designed with multiple levels: a Core level and multiples extra material. In addition students can choose to do the exercises in Pharo (with some bonuses) or Pharo and Java or simply in Java. The naming of the files, while looking chaotic, has a real meaning. When the file name contains - C019-W... it denotes the lectures from the Pharo mooc: http://mooc.pharo.org In particular it means that you can watch the videos for free. Remember this mooc is worth 150 K Euros. - Core means that the lectures will be given. - Extra it means that it is extra material for you that would like to learn more. In case we adapt some slides of the Mooc for the present lecture, they will have a similar name but both versions will be available to the students so that videos and presentations are always synchronised and this lecture contents is self-contained. The slides in Folder 00, are about the basics of OOP and they have companion videos http://rmod-pharo-mooc.lille.inria.fr/MOOC/2018-PreSequelOOP-FR/