The GNU Scientific Library (GSL) is a numerical library for C and C++ programmers. It provides over 1,000 routines for solving mathematical problems in science and engineering. Written by the developers of GSL this reference manual is the definitive guide to the library. The GNU Scientific Library is free software, distributed under the GNU General Public License (GPL). It is available for GNU (GNU/Linux), Unix and Microsoft Windows systems. This is the second edition of the manual, and corresponds to version 1.3 of the library.