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copied!<p>It will not run on other processors since 01010110011 means something on x86 and something else on ARM. x86-64 happens to be backwards compatible with x86 so it can run x86 programs.</p> <p>The binary is in a specific format that your OS understands (windows = PE, mac/linux = ELF)</p> <p>With any normal binary, your OS loads it into memory and populates a number of fields with certain values. These "certain values" are addresses to api functions that exist in shared libraries (dll, so) such as kernel32 or libc. The API addresses are needed because the binary itself does not know how to access hard drives, network cards, gamepads etc. The program uses these addresses to invoke certain functions that exist in your OS or in other libraries.</p> <p>In essence, the binary is missing some vital parts that need to be filled by the OS to make everything work. If the OS fills in the wrong parts, the binary won't work since they can't communicate with each other. That's what would happen if you would replace user32.dll with another file, or if you try to run a linux executable on mac osx.</p> <p>So how does libc know how to open a file?</p> <p>libc uses syscalls, which is low-level access to the OS core functions. It's sort of like a function call except you do it by populating certain CPU registers and then triggering an interrupt (special CPU instruction)</p> <p>So how does the OS then know how to open files?</p> <p>That's one of the things an OS does. But how does it know how to talk to a hard drive? I don't know exactly how that stuff works but I imagine the OS does this by writing/reading certain memory locations which happen to be mapped to BIOS functions.</p> <p>So how does the BIOS know how to talk to a hard drive?</p> <p>I don't know that either, I've never done any programming at that level. I imagine the BIOS is hardwired to the hard drive connectors and is able to send the correct sequence of 1 and 0 to talk "SATA" with the hard drive. It can probably only say simple things such as "read this sector"</p> <p>So how does the hard drive know how to read a sector?</p> <p>I really don't know this at all so I'll let some hardware guy continue.</p>

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