# Functions

A function is a built in formula. There are over 400 built in functions in Excel that can be accessed through the Insert Function button on the Formula Bar, or the Function Library on the Formulas tab.

After clicking the **Insert Function** button the Insert Function dialogue box appears.

Type in the name of the function, or select the relevant category to find the function you are looking for. A description of the function is displayed when a function is selected. Click **Ok**.

The Function Arguments dialogue box appears. Arguments are the information that the function needs in order to do its job.

The image below shows the arguments required for the IF() function. The argument in bold is mandatory, while the others are optional. When an arguments field is selected a description of what is required appears below.

As you become used to writing functions you may find it quicker and easier to write them directly into the cell. As you do so, Formula AutoComplete is displayed to assist you with finding the correct function and tooltips are displayed to prompt for the required arguments.

A function is made up of four parts:

- Equals sign =
- Function name i.e. SUM
- Parentheses
- Arguments (each argument is separated by a comma)