Sometimes, a bar is divided:

Sometimes, a bar:

Sometimes, a bar is divided into component parts, and the sum of all the parts equals the total length of the stacked bar. Pie charts use one or more circles divided into sectors to show the component parts of a whole. Presentation graphics software is very useful for analyst and decision makers, because it allows them to gain a better understanding of the relationships, changes, and trends that are buried in their numeric data This helps them in making more informed decisions.