you can see the diference between the code looking for system calls or HL API.
as Jdenny stated, assembly is hardware oriented. So you are programming at your pc, you are using IA-32 archicteture (a.k.a. Intel 32-bits). Basic instructions are connected to what Intel has specified on that (you can get book from Intel side).
--- there is some extensions to that archicture that arent present on every machine, such as SSE2 (intel) or 3DNow (AMD) ---
If u look thru the code, you will see eventually a system call/API. On that, you can identify the target platform (Win/*nix).