Each item on the Mac’s Desktop has a characteristic icon. The icon for an
individual file is kept within the file itself, but a custom icon for a folder is stored
as an invisible file inside the folder it adorns.
File Icons
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When a new application is added to your Mac the Finder looks inside the application file for associated icons. Usually there’s a whole suite of icons, one for each file type — such as a document, stationery or preferences file. The Finder then copies these icons into the Desktop file and keeps track of the application that goes with them.
When the Finder next displays a window containing the application’s files it extracts their icons from the Desktop file — this is quicker than getting them from the application!
If you add a custom icon to a file its Use Custom Icon attribute is automatically turned on — when the Finder sees this it uses the custom icon instead of the one in the Desktop file.
î If a custom icon is missing you should open a file utility such as FileTyper or Snitch
and check the Use Custom Icon attribute.
î Since custom icons aren’t in the Desktop file they’re not made available in memory
— they require disk access that slows down the Finder’s window display!
î If you add a custom icon to a file that’s visible in an open window it may not be
updated until you close the window and open it again!
î If you can’t see the correct icons on files associated with an application you may need
to restart your Mac and rebuild the desktop.
Icon Vaults
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  The suite of icons defined by an application can be replaced, in whole or part, by
using an icon vault — useful if you dislike the icons that came with an
application but don’t want to hack it about with ResEdit!
An icon vault is a special file, designed to suit a particular application. All vaults must be kept in a folder called _Icon Vaults (the name is preceded by a space) in the System Folder. Once the vaults are installed you should rebuild the Desktop — the vaults are then given priority over applications for supplying icons to the Desktop file.
î Since icons from an icon vault are actually in the Desktop file they don’t slow down
the display in the same way as custom icons!
√π See the Using ResEdit chapter for more about icon vaults
Folder Custom Icons
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  Folder custom icons are kept as invisible files inside their folder. They’ve no Type
or Creator codes and can remain on a disk drive even when their parent folder is
deleted — FileBuddy and other utilities can get rid of them!
Disks
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Disk Attributes
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  Disk attributes work in the same way as file attributes. When checked they have
the following effects:-
Inited
The disk is known to the Finder, which checks this attribute itself whenever it calls on it.
Use Custom Icon
A custom icon is in use, usually as a result of pasting an icon into the box in the Get Info window. Unfortunately this icon is replaced by the original icon in some dialogs! For more consistent results you should install a special drive icon using the formatting application supplied with the drive.
Name Locked
The name can’t be changed. In most instances, especially with a shared volume, or where applications are dependent on exact path names they shouldn’t be changed anyway.
‚à´ Disks can be locked using a special application called DiskLocker. This operates in
addition to the hardware lock on diskettes or other removable media.
Folders
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Folders are a really useful illusion. They don’t actually contain anything
— they only point to the files you want grouped together.
When an individual file is moved the disk’s Directory is modified but the file stays in the same place on the drive. Unlike files, folders can’t be locked.
Invisible Folders
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Files that are resident on the Desktop are actually contained within a invisible folder called the Desktop Folder. You can see and open this folder if you put your hard disk in an hierarchical menu — such a menu is provided by Apple Menu Options or OtherMenu.
Items in the Trash and Temporary Items are also in invisible folders that behave in the same way. Some hierarchical menus even let you to open files whilst they’re in the Trash!
Folder Attributes
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Folder attributes work in much the same way as file attributes. They have the effect shown when checked:-
Invisible
The folder can’t be seen.
Inited
The folder is known to the Finder, which checks this attribute itself whenever it calls on the folder. If you change other attributes, such as Invisible, it’s advisable to also uncheck Inited to to force the Finder to look at it.
Use Custom Icon
A custom icon is in use. You can do this by pasting into the icon in the Get Info window.
Name Locked
You can’t change the folder’s name.
Shared
The folder is being shared over a network
Suitcases
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  A Suitcase stores one or more files whose collective resources are available to the
system. Unlike a folder, whose files act as individuals, the contents of an entire
suitcase behaves in the same way as a single file.
You can drag files in or out of a suitcase but the process is different to moving files in or out of a folder. Hence the Finder presents a Moving… dialog whilst it copies the files into the suitcase and then removes the originals.
The following suitcase types may be encountered:-
Desk Accessory Suitcase
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  Rarely used in System 7 for storing a desk accessory (DA). The DA can only be
used after it’s dragged out of its suitcase. Older DAs can cause memory problems
if they’re not 32-bit clean and may lack a SIZE resource to indicate cleanliness!
Its DMOV code comes from Font/DA Mover, a pre-System 7 application that was used to load suitcases into the System file.
Type: DFIL Creator: DMOV
Font Suitcase
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  For storing fonts, usually within the Fonts folder in the System Folder. To avoid
confusion each suitcase should contain resources for just a single font family.
These font resources include a FOND (font family descriptor), accompanied by FONT (font description), NFNT (new font description) or sfnt (scalable font) resources that describe the font in detail. A vers (version) resource is often included for the Get Info window. All of these resources have information for each of the fonts in a suitcase.
Its FFIL Type means font file and its movr Creator comes from Font/DA Mover (see above).
Type: FFIL Creator: movr
System Suitcase
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  Used as a container for system sound files and keyboard layout files. The System
file itself, found in the System Folder, is the most common suitcase of this type.
Type: zsys Creator: MACS
Sound Mover Suitcase
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  Really a document created using the SoundMover application to store a number of
sounds. It’s not supported by the system so you can’t drag sounds in and out of it
— you must use the Sound Mover application to get inside the suitcase.
