## 11.4 Environment variables

There are three environment variables used by the Coq system. `$COQBIN` for the directory where the binaries are, `$COQLIB` for the directory whrer the standard library is, and `$COQTOP` for the directory of the sources. The latter is useful only for developers that are writing their own tactics and are using `coq_makefile` (see 12.3). If `$COQBIN` or `$COQLIB` are not defined, Coq will use the default values (defined at installation time). So these variables are useful only if you move the Coq binaries and library after installation.