Hello World in x64 assembly for Windows

; "C:\Program Files\NASM\nasm" -fwin64 hello64.asm
; "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\amd64\link" /LIBPATH:"C:\Program Files (x86)\Windows Kits\10\Lib\10.0.14393.0\um\x64" /SUBSYSTEM:CONSOLE /MACHINE:X64 /VERBOSE hello64.obj /ENTRY:_main /OUT:hello64.exe kernel32.lib

global _main
	extern GetStdHandle
	extern WriteConsoleA

section .data
	msg: db "Hello World!"

section .text
_main:
	mov		rcx, -11				; DWORD nStdHandle = STD_OUTPUT_HANDLE
	call	GetStdHandle

	mov		rcx, rax				; HANDLE hConsoleOutput = stdout
	mov		rdx, msg				; LPCVOID lpBuffer = msg
	mov		r8, 12					; DWORD nNumberOfCharsToWrite = 12
	xor		r9, r9					; LPDWORD lpNumberOfCharsWritten = nullptr
	sub		rsp, 40					; Reserve parameter space on stack
	mov		dword [rsp + 32], 00h	; LPVOID lpReserved = nullptr
	call	WriteConsoleA
	add		rsp, 40					; Clean up parameter space on stack

	xor		eax, eax
	ret