-> is a dereference operator. On line 65 (function ppm_create), f is declared as a pointer to a structure of type ppm (a reference to an object of type ppm). f

-> is a dereference operator. On line 65 (function ppm_create), f is declared as a pointer to a structure of type ppm (a reference to an object of type ppm). f is the actual structure/object. (f).w is the 'w' member of the structure. The brackets are needed for operator priority. f->w is another way to write (*f).w