Inside Macintosh: Files /

Chapter 2 - File Manager

Data Organization in Memory

This section describes the data structures used internally by the File Manager and any external file system that accesses files on Macintosh-initialized volumes. As described in "Data Organization on Volumes," which begins on page 2-52, most applications do not need to access these internal data structures directly. In general, you need to know about these data structures only if you are writing an external file system or a disk utility.

WARNING

This section is provided primarily for informational purposes. The organization of data in memory is subject to change. If you want your application to be compatible with future versions of Macintosh system software, you should not access these internal data structures directly.

The data structures maintained in memory by the File Manager and external file
systems include

• the file I/O queue
• the volume control block queue, listing information about each mounted volume
• the file control block buffer, listing information about each access path to a fork
• a B*-tree control block for the catalog file and the extents overflow file for each mounted volume
• the drive queue, listing information about each drive connected to the Macintosh

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Subtopics

The File I/O Queue

Volume Control Blocks

File Control Blocks

B*-Tree Control Blocks

The Drive Queue