A spreadsheet program is an electronic form of the accountant's worksheet. Cells may contain text, numbers, dates, or formulas. Files created with Excel are called worksheets . A formula is an instruction to perform a specific operation on one or more other cells. The cell would display the value 9.
Functions are predefined operations provided by the program.
They compute values and are very useful when constructing formulas. If, for example, you were maintaining a grade book, you might use the Average function to determine each student's grade average. Formulas are especially useful when the value of a cell depends on data in other cells that need to be periodically updated. If the cell contains a formula referring to those other cells, whenever the data are changed, the value of the cell containing the formula is automatically recalculated to reflect the changes. Using a function to compute averages.