For the stand alone solver you may specify a ** full
matrix ** in which you may later enter values for any or all of the
coefficients. Alternatively you may specify a ** semi-sparse **
matrix in which you identify coefficients which are nonzero. The values
of nonzeros may be entered into the spreadsheet cells later, but zero
coefficients cannot be changed and will always be zero.

For the embedded solver, coefficients and constants may be either numerical values or spreadsheet cell names (given as RnCm). Cell names must be given for all of the unknowns.

In summary the 3 options are:

- Stand alone solver with all cells changeable (`full matrix')
- Stand alone solver with some cells fixed as zero (`semi-sparse')
- Embedded solver with values or cells given for coefficients and cells given for solution