Mac OS X in a Nutshell

What Is Classic?

To help bridge the application gap between Mac OS 9 and Mac OS X, Apple has built a virtual machine that enables you to run older Mac software under Mac OS X in the Classic Environment, or just Classic. Classic is an emulator that looks and feels just like Mac OS 9, and, in fact, it is—just slightly watered down.

Classic allows you to run most older Mac applications on Mac OS X without requiring you to boot directly into Mac OS 9. The big difference is that Classic applications won’t benefit from the features of Mac OS X, such as protected memory and its advanced printing capability. Meaning, if a Classic application crashes, it could bring down everything else running under Classic; just as a crash under Mac OS 9 could affect your entire system.

Additionally, some Control Panels (

→ Control Panels), such as Control Strip, Memory, and Remote Access, are disabled. However, if you boot into Mac OS 9 instead of Mac OS X, you will be using a full version of the OS. See Section 3.8 later in this chapter for details on how to choose your Startup Disk.

If you want Mac OS 9 and Mac OS X on separate partitions, you will need to partition your hard drive and reinstall both systems. In most cases, the biggest benefit to installing Mac OS 9 and Mac OS X on separate partitions is being able to choose which version of the OS to boot at startup by holding down the Option key. ...