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Running Legacy Mac OS Applications: Classic

We all know what happened with New Coke and most of us (Coke drinkers at least) are probably pretty happy that we're still drinking Coke Classic. Unfortunately, the same can't be said for the Classic Mac OS. As we head toward the sixth year of Mac OS X's release, we still haven't closed the book on the original Mac OS operating system now called Classic.

The Classic environment is a complete implementation of Mac OS 9.x on top of Tiger. To Tiger, Classic is nothing but another application; to a user, however, Classic is a gateway to older Mac software programs.


You must have at least 128MB of memory to use Classic, an installed copy of Mac OS 9.x, and a 400MHz G3 (or faster) is recommended. Because Mac OS 9.x does not come with Tiger, you must order it from Apple.

When using the Classic environment, the 9.x operating system must access all hardware through the Tiger kernel. This means that software that accesses hardware directly will likely fail. Users of 3Dfx video cards, hardware DVD playback, video capture cards, and such are out of luck.

On a positive note, Classic brings the benefit of Tiger'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.


Classic does not gain all the stability features of Tiger, such as protected memory. If an application crashes in Classic, it can bring down all applications running in Classic. The overall system will be unaffected, but you might need to manually restart the Classic environment.

Working within the Classic environment is a somewhat unusual experience. Depending on the application running, there can be graphic anomalies and confusing filesystem navigation. It isn't perfect, but if you're a user who absolutely positively must run an old app, it'll do the trick.

Classic is typically launched once during a Tiger login session either manually or automatically. After it is running, Classic remains active until you log out or otherwise force it to shut down.

There are two ways to launch Classic: by double-clicking a Classic application or through the Classic System Preferences pane.

Configuring Classic Applications

Classic applications are automatically recognized by Tiger and treated slightly differently by the operating system. When using Get Info, the information panes change slight to display extended information and settings not required for native Mac OS X applications.

Identifying Classic Applications

In the Finder, Classic applications appear just like any other application. To verify that a piece of software is indeed a Classic application, you can select the icon and choose File, Get Info or choose Get Info from the contextual or action menus. Figure 2.55 shows the General Get Info pane for Key Caps, a Classic application.

Figure 2.55. The General Get Info pane identifies Classic applications.

Adjusting Memory Settings

Classic applications, because they still use the Mac OS 9.x Memory Manager, require a preferred and minimum memory size to be set. Because you have no direct access to the 9.x Finder under Mac OS X, Classic applications have an additional Get Info pane called Memory, as shown in Figure 2.56.

Figure 2.56. Classic applications allow memory limits to be set.

Two limits can be set:

  • Minimum Size The minimum amount of memory that an application must have to run. The Mac OS 9.x environment prohibits the application from launching unless the minimum memory size can be met.

  • Preferred Size The amount of memory that you want the application to have. This is the upper limit of the memory partition that will be requested from Mac OS 9.x.

To take advantage of the new Tiger memory architecture, set these values higher than you would in older versions of the Mac OS.

Forcing Carbon Applications into Classic

Carbon applications are a special case of Mac OS X application. They are capable of running natively on Tiger and on Mac OS 9.x through the use of CarbonLib. If you want to use the Classic environment to launch a Carbon application, a setting within the General pane of the Get Info pane can force a Carbon-compliant package to launch through Classic.

To launch a Carbon application in Classic, check the Open in the Classic Environment check box and then close the info pane. Subsequent launches will occur in Classic.

Controlling the Classic Environment

The operation and setup of the Classic environment is performed in the Classic system preference pane. The Start/Stop settings control how and when Classic boots, as demonstrated in Figure 2.57.

  • Select a Startup Volume for Classic Tiger can start the Classic environment by booting any available Mac OS 9.x system. Use this list to choose between any detected Classic-compatible systems.

  • Start Classic When You Log In If you want Classic to start up immediately after you log in to your computer (or immediately at startup, if you're using Tiger as a single-user system), click this button. Be warned: The Classic environment takes a few minutes to start, and your system performance will be degraded during this time.

  • Hide Classic While Starting The Classic startup window will be hidden while the Classic environment boots.

  • Warn Before Starting Classic Use this option to force Tiger to prompt you each time it launches the Classic environment. If you find yourself accidentally starting Classic by double-clicking legacy files, and so on, this can be helpful.

  • Show Classic Status in Menu Bar Adds a menu extra that can start and stop Classic and provides access to the Classic Apple menu items.

  • Start/Stop Click the Start button to launch Classic manually or Stop to shut it down.

  • Restart Equivalent to choosing Restart from the Mac OS 9.x Finder. Open applications prompt you to save open documents and then exit. The Classic environment will reboot.

  • Force Quit If Classic becomes unresponsive (that is, it crashes), the only option is to force it to quit. Open documents are lost, exactly as if Mac OS 9.x crashed (as it tends to do from time to time). You can also use the Control-Option-Escape keystroke to force it to quit.

Figure 2.57. The Classic System Preferences pane configures the startup volume and allows manual startup and shutdown.

Setting Advanced Startup Options

Use the Advanced settings pane to provide additional control over the boot sequence and basic Classic functions. You can make several modifications to the startup process and overall operation:

  • Turn Off Extensions Turning off the extensions is the equivalent of pressing Shift while booting into Mac OS 8 or 9. This prohibits additional control panels and extensions beyond those needed by the 9.x operating system from loading.

  • Open Extensions Manager This opens the Mac OS 9.x Extensions Manager control panel during the boot process, allowing you to disable extensions that appear to be causing system instability.

  • Use Key Combination This unusual option enables the user to choose up to five keys that will be kept in pressed state while Classic boots. Some extensions can be individually disabled by certain keystrokes; this feature lets you target those processes.

  • Use Mac OS 9 Preferences from Your Home If selected, Classic maintains a separate set of preferences for your account. If unchecked, a systemwide preferences location is used.

  • Put Classic to Sleep When It Is Inactive For When Classic is running, it is using your system resources. The Classic environment continues to use CPU time even if you aren't running a Classic application. This is because Mac OS 9.x must keep up the basic system maintenance and monitoring processes that happen behind the scenes. If you choose to put Classic to sleep, it stops using these resources after the length of time you choose.

  • Rebuild Desktop Rebuilding the Mac OS 9.x desktop can help solve "generic icon" problems (files that should have custom icons show up as generic white icons in the Finder), as well as issues with documents that can't find the appropriate Classic application to open them. If your Classic environment starts to act in unusual ways, rebuilding the desktop is a good place to start.


The first time you boot Classic, the advanced options will not be available. Subsequent executions will enable all the advanced features.

Viewing Memory Usage and Application Information

With Classic running, the Memory/Versions pane displays the processes that are active and how much memory they are consuming, as shown in Figure 2.58.

Figure 2.58. The Memory/Versions pane gives feedback on active Classic processes.

To display information about background Classic processes, click the Show Background Processes check box. Information about the version of Classic and its supporting software is displayed at the bottom of the pane.

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    Mac OS X Tiger Unleashed
    Mac OS X Tiger Unleashed
    ISBN: 0672327465
    EAN: 2147483647
    Year: 2005
    Pages: 251

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