The BLAS (Basic Linear Algebra Subprograms) are high quality "building block"
routines for performing basic vector and matrix operations. Level 1 BLAS do
vector-vector operations, Level 2 BLAS do matrix-vector operations, and Level
3 BLAS do matrix-matrix operations. Because the BLAS are efficient, portable,
and widely available, they're commonly used in the development of high quality
linear algebra software -- LINPACK and LAPACK, for example.

The original Fortran77 reference implementation of the BLAS is located in the
blas directory of Netlib.  However, this port uses the updated sources
distributed with LAPACK.

WWW: http://www.netlib.org/blas/