Editing Macintosh Toolbox (section)

=== ROM Organization ===
The Toolbox resides in ROM alongside the Mac OS kernel routines, occupying distinct memory regions based on the Macintosh model:

{| class="wikitable" style="width:70%; text-align:center;"
|+ '''Toolbox ROM Evolution'''
! Model !! ROM Size !! Toolbox Start !! Major Components
|-
| Macintosh 128K/512K || 64 KB || $400000 || QuickDraw 1.0, Core Managers
|-
| Macintosh Plus || 128 KB || $400000 || SCSI Manager, Hierarchical File System
|-
| Macintosh SE || 256 KB || $400000 || ADB Manager, improved QuickDraw
|-
| Macintosh II || 256 KB || $40800000 || Color QuickDraw, Palette Manager
|-
| Macintosh IIci || 512 KB || $40800000 || 32-bit QuickDraw, Sound Manager
|-
| Power Macintosh || 4 MB || $40000000 || PowerPC native code, 68k emulator
|}

The ROM is divided into functional modules, each containing related managers and their dispatch tables. Early ROMs were hand-optimized 68000 assembly code to fit within severe space constraints—the entire GUI framework, graphics engine, and system utilities compressed into just 64 KB.