PowerPoint lets you write on your slides while doing a presentation. For example, when in Slide Show view you can underline a specific point on a slide for more emphasis. You can do this using the Pen on the Pointer Options.

To use the Pen during your slide show:

1. Open your PowerPoint presentation.
2. From the View menu, click Slide Show.
3. Right click on a slide.
4. Point to Pointer Options and click Pen.

The mouse pointer will turn to a pen that you can use to draw on the slide. Once you are finished, press ESC and the mouse pointer will appear.