<P> A "spreadsheet program" is designed to perform general computation tasks using spatial relationships rather than time as the primary organizing principle . </P> <P> It is often convenient to think of a spreadsheet as a mathematical graph, where the nodes are spreadsheet cells, and the edges are references to other cells specified in formulas . This is often called the dependency graph of the spreadsheet . References between cells can take advantage of spatial concepts such as relative position and absolute position, as well as named locations, to make the spreadsheet formulas easier to understand and manage . </P> <P> Spreadsheets usually attempt to automatically update cells when the cells they depend on change . The earliest spreadsheets used simple tactics like evaluating cells in a particular order, but modern spreadsheets calculate following a minimal recomputation order from the dependency graph . Later spreadsheets also include a limited ability to propagate values in reverse, altering source values so that a particular answer is reached in a certain cell . Since spreadsheet cells formulas are not generally invertible, though, this technique is of somewhat limited value . </P> <P> Many of the concepts common to sequential programming models have analogues in the spreadsheet world . For example, the sequential model of the indexed loop is usually represented as a table of cells, with similar formulas (normally differing only in which cells they reference). </P>

3 types of data found in a spreadsheet