Regular C will start someplace in the runtime library, which will do things like global initialization. Once that's complete the library will call main(). The

Regular C will start someplace in the runtime library, which will do things like global initialization. Once that's complete the library will call main(). The OS determines the exact place in the code where execution starts. In DOS I think it was address 0x100. A more modern OS probably uses an executable file format that allows you to specify the starting address.