Classic Environment

From Mac Guides

Classic is a run-time environment for Mac OS X to permit applications written for Mac OS Classic — specifically Mac OS 9 — to run.

It operates by creating a virtual machine, and boots a modified installation of Mac OS Classic in that virtual machine.

Applications running in the Classic environment appear on the same desktop alongside Carbon and Cocoa applications, but retain their legacy appearance. Classic does not re-skin them to look like Mac OS X applications, although there are third-party software packages which can be used to do this.

The Classic environment allows a user to operate the vast majority of Macintosh legacy software — software that would not otherwise be able to run in Mac OS X. However, not all applications compatible with Mac OS 9 will run properly, or at all, in Classic. Software requiring specific, direct access to hardware may not operate as expected. The Classic environment can also be much slower with some applications than running them while booted directly into OS 9 on the same machine. On newer machines, however, these speed issues are not as profound.

Apple stopped supporting Mac OS 9 booting with the advent of Power Mac G4s with Firewire 800. These machines, along with Aluminum PowerBooks, G4 iBooks, and all G5-based machines must use Classic to run old software.

The final nail in the coffin of Mac OS 9-based software is that Apple is not supporting Classic at all on Intel-based machines.