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As most of us know, to create an Excel formula, you start by typing an equal sign: this distinguishes it from other types of data. A formula is made up of a series of expressions. There are three main components in these expressions: mathematical operations, such as addition and subtraction; functions; and cell references.
To create a formula which gives us the total of two of the numbers in a spreadsheet (say 24 and 12), we could simply type "=24 + 12". When we press the Enter key, we would get the correct result. However, the formula would have no link to the two cells containing the numbers. If the content of the cells were to change, the formula would still return the old result.
Obviously, the solution is to ensure that our formula contains a reference to the two cells in question. The simplest way of doing this is to click on the first cell having typed "=". Excel then automatically creates a reference to that cell. Next type the plus sign and click on the second cell. Excel creates a reference to the second cell and we then confirm the formula either by clicking on the Enter button (on the left of the formula bar) or pressing the Enter key on the keyboard.
Now that our formula contains a reference to these two cells, any time the cell contents change, the result returned by formula will be updated.
If this was the only way of performing calculations in Excel, formulas would very quickly become extremely long and very complex. To avoid this, we can use Excel's built-in functions. Functions perform complex mathematical calculations without us having to worry about how the result is arrived at.
For example, imagine that we wanted to add up the contents of a hundred different cells. If we relied purely on addition, we would end up creating a formula with a hundred different arguments; in other words, a hundred cell references to each of the cells containing the numbers. Thankfully, we can use the SUM function instead.
To include a function in a formula, type the equal sign followed by the name of the function. Next, type open brackets followed by the arguments of the function. The term arguments refers to the values required by a function in order to return a result. In the case of the SUM function, all we need to specify are the cell addresses of the numbers we want to total. We can do this automatically by clicking or dragging across each of the cells or ranges that contain those numbers.
When you have entered a reference to all cells containing numbers that we want to total, you can confirm entry of the formula by pressing the Enter key. You don't even need to close the brackets. Excel will close them for you.
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