Mac OS X Classic environment
The Classic environment provides a way for Mac OS X to run Mac OS 9 applications.
Classic essentially runs a copy of Mac OS 9 as an application on Mac OS X. You then run Mac OS 9 programs within Classic. The effect resembles the way you can run Windows programs within Virtual PC on a Macintosh.
A copy of Mac OS 9 is required for the Classic environment. If you do not have Mac OS 9 installed, you will need to install it before using Classic applications. You can do this if your computer -- or boxed copy of Mac OS X you purchased -- came with installation CDs for Mac OS 9.
Apple Macintosh systems and newer retail boxes of Mac OS X do not come with separate Mac OS 9 system disks. Newer computers -- particularly models released after January 2003, which cannot independently boot into Mac OS 9 -- should have Mac OS 9 available on their Software Restore discs, if you need to install it.
