Please read the Supplemental Material reading in Week 1. I've included the material in this module for those learners who might have missed it based on the course and Specialization they were currently enrolled in when the new versions of the courses and the new version of the Specialization went live. There's nothing graded in this module, the materials are just provided here so nobody misses any of the great stuff in the Specialization! Note that the exercise and programming assignment numbers are from a different course and have nothing to do with the exercise and programming assignment numbers listed in the four "real" weeks of this course.