Editing Mach-O (section)

=== Application main entry point ===

A load command starting with type {{code|0x00000028}} is used to specify the address location the application begins at.

{|class="wikitable"
|+ Load command (Main entry point)
|-
! Offset !! Bytes !! Description
|-
|  0 || 4 || {{code|0x00000028}} (Command type)
|-
|  4 || 4 || Command size (always 24 bytes)
|-
| 8 || 8 || Address location
|-
| 16 || 8 || Stack memory size
|}

If the segments/sections of the program do not have to be relocated to run, then the main entry point is the exact address location. This is only if the application segment addresses are added to an application base address of zero and the sections did not need any relocations.

The main entry point in a Mach-O loader is the program's base address plus the Address location. This is the address at which the CPU is set to begin running machine code instructions.

This replaced the old load command {{code|0x00000005}} which varied by CPU type as it stored the state that all the registers should be at before the program starts.