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Running Classic Mac OS Applications

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This chapter looks at the OS X Classic environment, how it works, how to configure it, and what to do if you absolutely must boot into Mac OS 9.x.
This chapter is from the book

This chapter is from the book

In This Chapter

  • The Classic Environment
  • Launching Classic
  • The Boot Process
  • Running Classic Applications
  • Maintaining and Monitoring Classic
  • Direct Booting Mac OS 9.x

If you've never had a Mac or are a NeXT user who's happy to have finally found a home, Mac OS X probably has more than enough available software and functionality to make you happy. Those of you who have been using the Mac operating system regularly for years, however, are likely to already have a software library that you rely on. To accommodate this need, Apple included the Classic environment. Classic provides a runtime layer for older, non-Carbonized Mac applications. It even allows certain pieces of hardware to be accessible, such as USB scanners and cameras. It is not a perfect solution, but it does allow for a high degree of compatibility with legacy hardware and software from within Mac OS X.

This chapter looks at the Classic environment, how it works, how to configure it, and what to do if you absolutely must boot into Mac OS 9.x.

The Classic Environment

As defined in Chapter 1, "Mac OS X Component Architecture," the Classic environment is a complete implementation of Mac OS 9.x on top of Mac OS X. To Mac OS X, Classic is nothing but another application; to a user, however, Classic is a gateway to his older software programs.


You must have at least 128MB of memory to use Classic, and a 400MHz G3 (or faster) is recommended. When it comes to Classic, more is definitely better.

Classic is a process under Mac OS X. Mac OS X must be running for Classic to work. In essence, you're booting two operating systems simultaneously.

When using the Classic environment, the 9.x operating system must access all hardware through the Mac OS X kernel. This means software that accesses hardware directly will fail. Users of 3Dfx video cards, hardware DVD playback, video capture cards, and even some CD writers will find that their hardware no longer functions correctly.

On the other hand, Classic brings the benefit of Mac OS X's virtual memory underpinnings to legacy applications. Each Mac OS 9.x application can be configured for a much larger memory partition than was possible previously. To the Classic environment, the virtual memory appears to be real memory. Programs have much more breathing room in which to function.

Working with the Classic environment is a somewhat unusual experience. Depending on the application running, there can be graphic anomalies and confusing file system navigation. This chapter will show what you'll see and what to do when things don't seem to work right.

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