Editing Spreadsheet (section)

=== Spreadsheet programs ===
A '''''"spreadsheet program"''''' is designed to perform general computation tasks using spatial relationships rather than time as the primary organizing principle.

It is often convenient to think of a spreadsheet as a mathematical [[graph theory|graph]], where the [[node (graph theory)|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.

Spreadsheets usually attempt to automatically update cells when the cells 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 cell formulas are not generally invertible, though, this technique is of somewhat limited value.

Many of the concepts common to sequential programming models have analogs in the spreadsheet world. For example, the sequential model of the [[For loop|indexed loop]] is usually represented as a table of cells, with similar formulas (normally differing only in which cells they reference).

Spreadsheets have evolved to use [[Scripting language|scripting]] programming languages like [[Visual Basic for Applications|VBA]] as a tool for extensibility beyond what the spreadsheet language makes easy.