When a cell contains a formula, it often contains references to other cells. Such a cell reference is a type of variable. Its value is the value of the referenced cell or some derivation of it. If that cell in turn references other cells, the value depends on the values of those. References can be relative (e.g., codice_13, or codice_14), absolute (e.g., codice_25, or codice_26) or mixed row– or column-wise absolute/relative (e.g., codice_27 is column-wise absolute and codice_28 is row-wise absolute).