Options - Excel

(Formulas tab, Workbook calculation) - Lets you change the if a workbook is calculated automatically when a workbook is opened or saved or whether it is done manually using F9. If you have a large worksheet containing complex functions then it may be worth changing your calculation mode to Manual.
(Formulas tab, Recalculate workbook before saving) - Calculates all dependent formulas in the worksheet before it is saved.
(Formulas tab, Enable iterative calculation) - This allows you to perform an iterative circular reference.
(Formulas tab, Maximum iteration) - The number of times a formula is calculated until the result is obtained.
(Formulas tab, Maximum change) - This is the maximum number of iterations the workbook will perform to resolve formulas when the workbook is re-calculated.
(Formulas tab, R1C1 reference style) - Displays your columns as numbers and not as letters.
(Formulas tab, Formulas inconsistent with other formulas in the region) - Select to have Excel treat a formula in a region of your worksheet that differs from the other formulas in the same region as an error and to display a warning.

(Advanced tab, Editing Options)(Extend data range formats and formulas) - Formulas that contain references to ranges will be automatically expanded when new cells are inserted to the right or below the existing range. This only works when cells are inserted immediately below or to the right of a referenced range.
(Advanced tab, Editing Options)(Allow editing directly in cell) - If you switch this option off you will not be able to edit your cells directly in the cells but will have to use the Formula Bar. When you double click a cell, instead of being taken into edit mode all the cells that are directly referred to in the formula will be selected. An alternative is to press F2.
(Advanced tab, Display options for this worksheet)(Show formulas in cells instead of their calculated values) - Displays all the formulas on the active worksheet. All the columns will double in width.
(Advanced tab, Formulas)(Enable multi-threaded calculation) - Selected by default, this option enables fast calculation by using all of the processors on your computer, or by using the number of processors that you type manually.
(Advanced tab, General)(Ask to update automatic links) - Displays a confirmation message asking if you want to update the links whenever a workbook containing external links is opened.
(Advanced tab, General)(Enable multi-threaded processing) - This controls all multi-threaded operations (except calculation). This includes sorting, row height calculations and finding the best fit for column widths. This option is not available in the object model. Selected by default but you need to have a multi-threaded processor.