Packed storage matrix

A packed storage matrix, also known as packed matrix, is a term used in programming for representing an formula_1 matrix. It is a more compact way than an m-by-n rectangular array by exploiting a special structure of the matrix.
Typical examples of matrices that can take advantage of packed storage include:
Code examples (Fortran).
Both of the following storage schemes are used extensively in BLAS and LAPACK.
An example of packed storage for hermitian matrix:
An example of packed storage for banded matrix: