An alias is a pointer to an icon. The icon can be anything: a document, application, INIT, folder, disk, file server -- even another alias. A file can have an infinite number of aliases. Aliases let you refer to documents, folders, and applications with minimal impact on disk space, but with maximum convenience of location.
An alias is a small file that "remembers" the location of the original file, rather than containing the same data as the original. An alias file is typically 1K or 2K.
Once an alias is created, either the alias or the original may be moved to another location, although the original must stay on the same volume it was on when the alias was created. The name of the alias is always in italic and has the same icon as the original file. You may change the name of the alias without affecting the original file. When you wish to open the original, double-click the alias and the system responds as if you had double-clicked the original.
Where You Can Place Aliases
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When making more than one alias of a file/application, you can place them in a variety of locations for convenient opening, such as the Apple Menu folder in your System folder and the folder containing the application used to create the file.
By placing an alias of files, applications, sounds, QuickTime movies, and so on in the Startup Items folder in your System Folder, these items are automatically launched at startup. If you don't want them to load, just hold down the Shift key at startup.
Connecting to a File Server
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To quickly connect to a File Server over a network, make an alias of the File Server while you are connected to it and drag the alias to some convenient place on your hard drive. For example, place the alias in the Apple Menu Items folder in your System folder and you can then access the File Server directly from the Apple Menu.
Removable Media
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Aliases let you locate files on removable media such as floppy disks, CD-ROM discs, or removable cartridges. All you have to do is make an alias of the file(s) on the removable media and place the alias on your hard disk. When you double-click on the file's alias, you are asked for the disk by name that contains the original file. This also works with compression software used in archiving files to floppy disks.
Using Aliases With Remote Access
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To create an alias over an Apple Remote Access connection, select the alias icon of the remote, mounted hard drive. Choose Get Info from the File menu, then click the Locked checkbox. If you do not lock the alias, the alias can be converted to call the wrong Apple Remote Access server or to try to access the service across your local network.
Aliases and Upgrading Systems
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If you upgrade an existing Macintosh (such as from a Quadra 700 to a Quadra 800) and name the new machine the same name as the old machine, the existing aliases continue to work. They continue to work, as long as the machine and the volume are named the same on the Quadra 800 as they were on the Quadra 700.
The explanation of how aliases work is a little bit longer. The first step in resolving the alias is to identify the volume on which the target resides. Thus, the alias stores some volume mounting information, such as the server and zone information. The zone name and the server name must be the same in order for the alias manager to successfully resolve the alias. Additionally, if the volume is not a local volume (as is the case in this situation), the volume name must be the same.
Once the correct volume is found, there are a number of ways that the alias manager can resolve an alias. One piece of information that it uses is the file (or directory) ID. Using this, if the file moves somewhere else on the volume, the alias is able to locate it. Additionally, the alias manager uses the location and file name to resolve an alias.
When an alias is created, the file ID of the actual file, is saved within the alias record. When you then copy the actual file to another location (such as to a new drive), the file ID of the "new", copied application is different than the original application's file ID. The alias record still contains the original application's file ID. If the alias manager fails to resolve the alias by using the file ID, it attempts to use the relative path name to resolve the alias. As long as the path to the file remains the same, the alias is able to be resolved.
Once an alias is used, the alias record is updated with any information that had changed. For example, if the file ID had changed (because it was a copy of the original), once the alias is used, the new file ID is stored with the alias. After that, the file can be moved around, and the alias is still able to find it.
The bottom line is, you can copy an entire hard drive from one system to another (such as the Quadra 700 to the Quadra 800). As long as you name the machine the same in Sharing Setup, name the volume the same, and do not move any of the files (or applications) that have aliases to them, at least until all of the aliases are used, and updated, everything should work correctly.
If An Alias Fails to Work
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If you open an alias and nothing happens, or you see a message reporting that the original file is not available, it means that the alias is damaged, or the original was removed. Aliases are not removed when the original icon is removed.
First, try to locate the original of the alias using the Find Original button in the Info box of the alias (or you can use the Find command). If the original still exists and the alias does not work, remove the defective alias then select the original and make another alias of it.
If you cannot locate the original file, it may have been deleted (file or folder) or unmounted (volume); or there may be a break in the network, and the alias has been left pointing to a location that contains nothing.
Article Change History:
14 Feb 1995 - Updated keyword.
08 Feb 1995 - Added keyword; combined several articles; updated for System 7.5.
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