This book covers the following two themes: 1. GC Algorithms (Algorithms Section) 2. GC Implementation (Implementation Section) The Algorithms Section introduces a carefully selected group of important GC algorithms from the many that have been devised. It includes both traditional and fundamental algorithms, as well as some more advanced ones. The main goal of the Algorithms Section is to help you understand the unique way of thinking about GC and the characteristics of each algorithm. In the Implementation Section, we will delve into the GC of a language processing system selected by the authors. The idea is to thoroughly learn the theory in the Algorithms Section and then see how that theory is actually used in practice in the Implementation Section.