How to change screen size?

How do i change my screen size back to where it takes up the whole screen?

• My monitor can be used as a T.V. or as a computer and now im using it as a computer and the screen stretched from corner to corner of the entire screen but now the sides have been cut so the screen it smaller and it makes the browsers and other applications on my computer have larger print and less open space as it did. How can i change it back? I'm not sure how i changed it in the first place

• Answer:

  If you have windows 7 rick click on the desktop and click display and change the resolution if not then go into the control panel and look for a display settings thing if you dont have that go into your video cards control panel thing for example ATI catalyst and change the screen resolution from there