You may have noticed the command \label as part of the figure commands in the previous task - it is very useful, not only for inserting pictures in your document. This command works as a label. When we write documents we quite often have to refer to an images, a chapter or an equation, and we call that a cross reference. If you label chapters, figures, equations, etc., it will make the job of referencing much easier. The cross references are automatically updated if you move content within your document, so if you move a figure you will not have to manually change the figure's number in the figure text or the places where you reffered to it. Remember that each label must be unique!

This system might be easier to understand when you try it out yourself, here is an example of how you can use labels and cross references.

How to insert a cross reference

As you can see, the command \ref{fig:laptop_writing} in the source file gives ut the number 1 in the pdf file. This is because it is the first image in this document. It might seem a bit much work to write \ref{fig:laptop_writing} in stead of 1, but imagine when you want to insert more images, and also rearrange them. Then you will not have to change the numbers yourself, they will change automatically. That also goes for anything else you label.

Task

Insert one or more cross references into your document and notice how the numbers are updated automatically as you add them. Use the picture above to see how it is done.