 In an effort to bootstrap the GNU operating system, Richard Stallman asked Andrew S. Tanenbaum, the author of the Amsterdam Compiler Kit (also known as the "Free University" Compiler Kit) for permission to use that software for GNU.When Tanenbaum advised him that the compiler was not free, and that only the university was "free", Stallman decided to write a new compiler.Stallman's initial plan was to rewrite an existing compiler from Lawrence Livermore Laboratory from Pastel to C with some help from Len Tower and others.