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.

A Fortran77 reference implementation of the BLAS is located in the blas
directory of Netlib.

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