Editing Macintosh Toolbox (section)

=== Resource Manager ===
The Resource Manager provides a two-level virtual memory system for code and data, searching multiple resource files in a defined order:

'''Resource File Structure:'''
<pre>
Resource Header (256 bytes):
    Data offset:        4 bytes
    Map offset:         4 bytes
    Data length:        4 bytes
    Map length:         4 bytes

Resource Map:
    Header copy:        16 bytes
    Next map handle:    4 bytes
    File ref number:    2 bytes
    Attributes:         2 bytes
    Type list offset:   2 bytes
    Name list offset:   2 bytes
</pre>

'''Resource Attributes (bit flags):'''
* '''Bit 0''': System reference (resSysRef)
* '''Bit 1''': Preload at startup (resPreload)
* '''Bit 2''': Protected from changes (resProtected)
* '''Bit 3''': Locked in memory (resLocked)
* '''Bit 4''': Purgeable from memory (resPurgeable)
* '''Bit 5''': Load into system heap (resSysHeap)

'''Search Order:'''
# Current resource file (most recently opened)
# Application resource fork
# System file resource fork
# ROM resources (if not overridden)