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10 Glossary

Allocation block: this is a block of file data within the file space of a volume. The size of allocation blocks is the same within a volume, but different volumes can have different allocation block sizes. This size is always a multiple of 512 bytes so allocation blocks boundaries are always aligned with logical blocks.

Creator type: Associated with every file on a Mac is a four letter code that specifies the file’s creator. The creator is typically the application that created the file to begin with. This code is hidden from the user, but is used by the file system in a number of ways. For one, along with the File type, it helps determine the icon to display for that file. In addition, when you double click on a document, it is the application that has the same creator code as the document that will be launched to open that document.

File type: Associated with every file on a Mac is a four letter code that specifies the type of file it is (e.g. ‘TEXT’ denotes a text file, ‘APPL’ denotes an application). On many other operating systems, the file type is part of the name; it is usually a three-letter code following a period (e.g. myfile.txt or letter.doc). On the Mac, this code is hidden from the user but serves the same purpose: to identify the kind of file. It uses the file type, along with the Creator type (see below) to determine the icon to display for a given file.

HFS, HFS+: This stands for “Hierarchical File System” and “Hierarchical File System – Plus”. These are the names of Apple’s proprietary File system layout for Mac OS computers. The newer, HFS+ system affords greater file and disk capacities, as well as performance improvements over that of the older HFS architecture. HFS+ was released with Apple’s 8.1 operating system and is designed to supersede HFS. All Mac OS versions from 8.1 Classic through OS X 10.x support both HFS and HFS+.

Orphan: An orphaned file or folder is a file or folder which Data Rescue has discovered a catalog entry for, but no parent catalog folder can be found. Items like this are presented under the Orphans Folder in the Data Rescue recovery window.

Physical block: this is a 512-byte block of information on a physical device. Physical blocks start at zero so physical block #0 is usually the first block of the partition map of a physical device.

Remote volume: A remote volume is a volume that is not directly connected to your computer. Typically a remote volume is a file server. If your Mac is not connected to a computer network (e.g. at your company), you probably don’t have access to any remote volumes.

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