This comprehensive reference manual documents how to use the GNU compilers, as well as their features and incompatibilities, and how to report bugs. It corresponds to the compilers (GCC) version 7.0. As the project became so big project over the years, we had to split this reference manual in two parts that are two separate physical books. To keep it consistent with the digital manual, the references and page numbers cover both physical books as it were one. Therefore please note that you probably want to have both parts.