Another lovely feature of Mac OS X is the ability to magnify the screen no matter which application you might be using.  This is a feature that is usually enabled via the Universal Access control panel.  To access it, you would go to the Apple Menu located in the top left corner of your screen, select System Preferences and then look for the Universal Access panel.  The zoom feature is usually located in the seeing section of the Universal Access panel.  You should ensure that Zoom is enabled.

If you are using a scroll mouse, you can hold down the Control Key and use the scroll button on your mouse to zoom the whole screen in and out.  You can, in fact, configure which modifier key you wish to use, if you prefer not to use the Control Key.

If you are using a MacBook or MacBook Pro, you can use the Control Key with the Two Finger Scroll to achieve the same zoom result.  You need to enable this feature in Universal Access also.  The Universal Access panel is also sometimes named Accessibility.

The beauty of this zoom feature is that it zooms the entire screen, so it does not matter what you are looking at or which program you are using.  You can also choose the Zoom In Window option which effectively gives you a small floating window that moves with your mouse arrow and magnifies everything it finds underneath - a bit like a big magnifying glass.  This is very useful for magnifying only certain parts of the screen at a time.

You can also use command keys to switch the Zoom feature on and off, as well as to zoom in and out.  To toggle the Zoom feature on and off, use CMD+OPTION+8 (the option key is sometimes called the ALT key).  To Zoom In, press and hold the CMD key and the OPTION key and then press the = key repeatedly to zoom in more and more.  To Zoom Out, do the same thing but pressing the key instead.