AnyonewhohaseverreadapieceofCsourcecodehasseenthem—thepreprocessordirectives.Forexample,youcanfindincludedirectives(#include)atthebeginningofmostsourcefiles.Thepreprocessorisasystemthatrewritesthesourcebeforetheactualcompilerseesit.Clearly,thisisaverypowerfultool—thedownsideisth