If the coefficient matrix 
is sparse, large-scale linear systems
of the form 
can be most
efficiently solved if the
zero elements of are not stored. Sparse storage schemes allocate
contiguous storage in memory for
the nonzero elements of the matrix, and perhaps a limited number of
zeros. This, of course, requires a scheme for knowing
where the elements fit into the full matrix.
There are many methods for storing the data (see for instance Saad [186] and Eijkhout [87]). Here we will discuss Compressed Row and Column Storage, Block Compressed Row Storage, Diagonal Storage, Jagged Diagonal Storage, and Skyline Storage.