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copied!<p>The easy way to find out is to stick a breakpoint in <code>main()</code> and take a look:</p> <p><img src="https://i.stack.imgur.com/vDJAu.png" alt="call stack"></p> <p>So technically, the answer to the question is that <code>main()</code> is called from something called <code>start</code>. You don't get the source code for <code>start</code>, but you can look at the assembly code in the debugger if you want. This version is from code built for the simulator:</p> <pre><code>0x1c30: pushl $0 0x1c32: movl %esp, %ebp 0x1c34: andl $-16, %esp 0x1c37: subl $16, %esp 0x1c3a: movl 4(%ebp), %ebx 0x1c3d: movl %ebx, (%esp) 0x1c40: leal 8(%ebp), %ecx 0x1c43: movl %ecx, 4(%esp) 0x1c47: addl $1, %ebx 0x1c4a: shll $2, %ebx 0x1c4d: addl %ecx, %ebx 0x1c4f: movl %ebx, 8(%esp) 0x1c53: movl (%ebx), %eax 0x1c55: addl $4, %ebx 0x1c58: testl %eax, %eax 0x1c5a: jne 0x00001c53 ; start + 35 0x1c5c: movl %ebx, 12(%esp) 0x1c60: calll 0x00001c70 ; main at main.m:9 0x1c65: movl %eax, (%esp) 0x1c68: calll 0x00002376 ; exit 0x1c6d: hlt 0x1c6e: nop 0x1c6f: nop </code></pre> <p>If you create a MacOS X command-line program and put a breakpoint in <code>main()</code>, you'll find that <code>main()</code> is called by <code>start</code> on the desktop, too. The assembly for the Mac version of <code>start</code> isn't exactly the same, but it's very close. So it's a good guess that <code>start</code> is generated for you by the compiler based on the target platform, and that <code>start</code> is the entry point that the operating system looks for when it's launching a program.</p>

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