System Folder

The System Folder on on a startup disk contains all your system software. This must contain at least a System file and Finder file, as well as other essential files. Note that:-

  1. There should only be one System Folder on your startup disk.
  2. The active or blessed System Folder carries a small Mac symbol. If you remove the System file in such a folder it becomes inactive and the symbol disappears. If a folder loses its Mac icon just drag the System file out of the folder and then put it back again.
  3. The System Folder can be renamed, although this isn’t advisable.

The System Folder is created and filled with various items during the installation of the system. However, if you install extra software onto your machine other folders and files can appear.

Files stored in the System Folder can stay active even when dragged out of their folder. For example, a control panel kept outside the Control Panels folder but left ‘loose’ in the System Folder can remain active even after a restart. To make files inactive you must either move them to the appropriate (Disabled) folder in the System Folder or remove them entirely from the System Folder. You should then select Special ➡ Restart in the Finder.

System Folder Items

The items listed below are sometimes found in the System Folder. Don’t worry if you don’t have all these items, as the folder’s content varies with the Mac OS and other software that’s installed.


This folder contains folders such as Desktop Pictures, Sound Sets and Theme Files, all of which contain files used by the Appearance control panel. Any unwanted files can be removed.

Apple Menu Items

This folder contains all the items that appear in the Apple menu. As well as items provided during installation, it can hold aliases of other items that you require (see below). If the Apple Menu Options control panel is enabled each folder in this folder appears as a submenu in the menu.

Apple MIDI Driver

A very old driver file that forms part of Apple’s MIDI Manager package, allowing a simple MIDI interface to be connected either of the serial ports on a ‘classic’ machine.

Application Support

This folder contains ‘private’ extensions, libraries or plug-ins that are only used by specific applications. Applications designed prior to Mac OS 8.x don’t use this folder, although there’s nothing to stop you adding files to the folder if your application accepts them in this location.


This folder contains files used by products produced by Claris and other companies, including AppleWorks (formerly known as ClarisWorks), some versions of FileMaker Pro, and earlier versions of MacLink Plus, all of which use the Claris XTND file translation system. ClarisWorks also uses this folder for its help system, as well as for file translators and other documents.


Contains the last item that you copied or cut. Data is often stored in an application format as well as a standard format such as TEXT or PICT. Although clipboard data is also kept in memory for fast access, some applications have a private clipboard in their own memory areas. Others applications must then use the Clipboard file instead, increasing disk activity and slowing down the operation. Other complications can occur if you use a special extension to provide multiple clipboards.


This folder is provided when you install an application that uses colour profiles employed by the Kodak Precision Colour Management System (KPCMS).

ColorSync Profiles

This folder contains profiles used for the ColorSync colour matching system.

Contextual Menu Items

This folder contains contextual menu plug-ins, also known as contextual menu modules (CMMs), each of which provides one or more items that appear in contextual menus. These menus are shown when you Control-click (or right-click a two-button mouse) in an appropriate location.

Control Panels

This folder contains enabled control panels, sometimes known as a control device (cdev). Some of these contain INIT resources that modify the Mac OS during startup, often increasing the machine’s memory requirements, but also adding extra features to the system.

Control Panels (Disabled)

This folder that contains control panels that are disabled, which usually means they’re out of operation. Such files have either been dragged out of Control Panels or have been deselected using an extensions management utility, usually the Extensions Manager control panel.

Control Strip Modules

This contains control strip modules that can be used whenever the Control Strip control panel is enabled. Typical modules supplied with the system include AppleTalk Switch, Battery Monitor, CDStrip, Energy Settings, File Sharing Strip, Monitor BitDepth, Monitor Resolution, Printer Selector, Sound Volume and Video Mirroring. Shareware offerings are also available.

DataViz folder

Contains file translators, as used by older versions of DataViz’s MacLinkPlus and made available to the File Exchange control panel.

Debugger Prefs

This file is required for MacsBug (see below) when used with non-US versions of the Mac OS.


This folder contains part editors used by OpenDoc for data handling, although most users won’t require these items since OpenDoc is obsolete. When you install an OpenDoc part it adds an additional set of part editors, usually within a specific folder inside this folder. This folder also contains an OpenDoc folder that contains OpenDoc Shell Plug-Ins and OpenDoc Libraries folders, the latter containing the OpenDoc application itself and associated library files.


This folder contains extension files that add functionality to the Mac OS, as indicated by their jigsaw icons. These documents include printer files that tailor data for specific printers, network software for systems such as Ethernet, and communication tools for serial links and modems.

The most common extensions are system extensions and Chooser extensions. Many system extensions contain INIT resources that modify the system at startup, invariably using up memory.

Extensions (Disabled)

Contains disabled extensions, which have been dragged out of the Extensions folder or have been deselected by means of an extensions management utility such as Extensions Manager.


This folder contains aliases of items that appear in the Favorites menu of file dialogues in modern applications. Unfortunately, this isn’t shown in older applications that don’t support Navigation Services. You can add items to the Favorites menu by dragging aliases into this folder or by Control-clicking (or right-clicking) on the items and choosing Add to Favorites.


This is really a special application, launched at startup, that creates the Mac’s desktop, links each document to its parent application and presents each item with its correct icon.


This folder contains the fonts available to your system and applications. There can be up to 128 font suitcases, each holding any number of fonts up but limited to a total size of 16 MB. Some of these suitcases may be accompanied by Type 3 outline font files for PostScript printing.


Contains Apple’s Help Viewer application and associated help files.

Internet Plug-Ins

This folder contains plug-ins that are available to any suitable Web browser on your computer. Although most browsers have their own Plug-ins folder, only those plug-ins placed in this ‘global’ folder are available to all browsers. To save disk space you should put all your plug-ins here.

Internet Search Sites

A folder containing plug-ins used by Apple’s Sherlock application for searching the Internet. You can obtain more of these from the Internet itself.


Contains files used by the Kodak Precision Colour Management System (KPCMS).

Launcher Items

Contains items, preferably as aliases, that appear in the Launcher window when the outdated Launcher control panel is enabled. Any folder whose name has a prefix appears as a category button at the top of the window. You can remove this folder if you don’t use Launcher. As it happens, Mac OS 8.x and later systems incorporate most of the features provided by this panel.


This is actually a control panel, but resides here for purely historic reasons. Although the original Mac TCP panel, as used for the Internet, has been replaced by Open Transport software, many applications still expect this file at this locations. The letters DNR stand for Dynamic Name Resolver.


An optional debugging application that’s used by developers. It’s automatically launched following any system crash, although it can also be activated using a special key combination.

MS Preferences Panels

Contains special files used by older versions of Internet Explorer and Outlook Express.

Note Pad File

Contains the text stored in the Note Pad application found in older versions of the system.

PatchBay Help

A very old file forming part of Apple’s MIDI Manager package and designed to work with its PatchBay application. This file can be placed alongside the PatchBay application if preferred.


This folder contains preferences files, sometimes identified by a ‘buttons’ icon and containing settings for an application or control panel. The removal of a corrupted preferences file can often fix a problem. For example, throwing away the Finder Preferences file can cure bad behaviour in the Finder, such as desktop views not ‘sticking’, or a flashing ‘Happy Mac’ or ‘empty box’ at startup.

Some applications use a subfolder for each set of preferences, such as the Extensions Manager Preferences folder. Similarly, the Printing Prefs folder has settings for each printer you’ve used, usually accommodated by a number of PICT files that are designed as watermarks for printing.

The Preferences folder can contain other folders, often created by an installer, that store special resource files used by an application, although these are less common with modern applications.

Printer Drivers

This folder is designed for modern printer software, although its usually found to be empty.

PrintMonitor Documents

This contains printer files for documents that are awaiting printing, as used by the PrintMonitor or Desktop PrintMonitor applications when background printing is selected in the Chooser.

Scrapbook File

This file contains all the items that appear in the Scrapbook application. If you use an alternative application you can remove this file.

Scripting Additions

This folder contains files that extend the basic capabilities of AppleScript. Those additions provided during installation of the last system should never be removed as they’re used by the Mac OS itself.


This contains folders of compiled AppleScript scripts, including a folder called Folder Action Scripts. The latter shouldn’t be removed as it’s used by the Mac OS. However, you can move the entire Scripts folder to your Documents folder and then create an alias of the folder at this location.


This folder should contain files used for servers on a network, although it’s usually empty.

Shutdown Items

This folder contains items, preferably in the form of aliases or AppleScript applets, that are opened in alphabetical order when you select Special ➡ Shut Down.

Shutdown Items (Disabled)

This contains items that have been dragged out from the Shutdown Items folder or have been disabled by means of the Extensions Manager control panel.

Startup Items

This folder contains items, preferably in the form of aliases or AppleScript applets, that are opened in alphabetical order when your computer starts up. This could, for example, include an alias of a clippings file that you want to appear on your desktop every day.

Startup Items (Disabled)

This contains items that have been dragged out from the Startup Items folder or have been disabled by means of the Extensions Manager control panel.

Startup Movie

An optional file, in the form of a standard QuickTime movie file, that runs at startup. The movie can be stopped at any time by pressing any key. The file must have this exact filename.


An optional file containing a PICT resource graphic that appears on your Mac screen in place of the Welcome to Macintosh window at startup. The file must have this exact filename.


This file contains the code that makes your machine work. It includes routines called ROM patches that replace any outdated software that originally existed in the machine’s ROM. The System file also contains resources that are revealed when you double-click its icon. These items can be moved in and out of the System in the same way as a folder. These resources include alert sounds used by the Sound control panel and keyboard resources used by the Keyboard control panel.

If the System file is damaged you may suffer from the following problems:-

Your Mac will also run slowly if the System file is fragmented across the disk drive.

System Extensions (Disabled)

Contains other files normally resident in the System Folder, but disabled by Extensions Manager.

System Resources

This contains extra resources that make your machine’s hardware compatible with the current version of the Mac OS. You may find this file appearing or disappearing when you next update your system.

Text Encodings

This folder contains files, often used by Internet applications such as Internet Explorer, that accommodate the different character coding systems employed in various parts of the world, including ISO Latin-1, Windows Latin-1 and Unicode. This folder and the Text Encoding Converter in the Extensions folder, are essential for HFS+ to be used for disk formatting.

Trimming the System

Generally speaking, if you have a modern machine with sufficient memory and disk space, you should leave your System Folder alone. However, if you know what you’re doing, you can remove or relocate selected files to reduce system overheads.

Disabling the following control panels can save memory, assuming you can do without them:-

AppleTalk, CloseView, Easy Access, File Exchange, Mac OS Easy Open, PC Exchange, ˜ ATM

The following extensions can also be disabled in some instances:-

CFM-68K Runtime Enabler, AppleShare, ColorSync, Color Picker, File Sharing Extension, Foreign File Access, Network Extension, Printer Share, PrinterShare GX, QuickDraw GX, QuickTime

You’ll normally need to select Special ➡ Restart in the Finder after disabling such files.

©Ray White 2004.