Simple MASM program to output hello world

helloworld.asm

; NOTE: to successfully build you must have a copy of kernel32.lib in the same directory!
; build:
; ml64 helloworld.asm /link /subsystem:console /entry:main

includelib kernel32.lib           ; library - kernel functions (Windows Kit) (directory relative)

; external functions and handles
GetStdHandle            proto     ; function - gets an output handle
WriteConsoleA           proto     ; funciton - writes to a console handle
ExitProcess             proto     ; function - exits the current process
SetConsoleTextAttribute proto     ; function - set text attributes for file
Console                 equ   -11 ; handle - defualt handle for the current console

    .data
msg           byte  "Hello, World!", 0Ah, 0Dh   ; null-terminated string of bytes
stdout        qword ?                           ; reserves space for handel to stdout
nBytesWritten qword ?                           ; reserved space for the number of bytes written

    .code
main proc
    sub  rbp, 40                   ; create a 40-byte frame on the stack

    ; get file handle for Console
    ; filehandle GetStdHandle(RCX)
    mov  rcx, Console              ; move Console value to RCX (console handle)
    call GetStdHandle              ; gets handle for Console and puts it into RAX
    mov  stdout, rax               ; store the handle in 'stdout'

    ; set bgcolor and fgcolor text attributes
    ; void SetConsoleTextAttribute(RCX, RDX)
    mov  rcx, stdout               ; RCX (arg 1) - file handle
    mov  rdx, 1fh                  ; RDX (arg 2) - bgcolor = 0x1 (Blue), fgcolor = 0xf (Bright white)
    call SetConsoleTextAttribute   ; call the function (no return)  

    ; displays the message in the console
    ; void WriteConsoleA()
    mov  rcx, stdout               ; RCX (arg 1) - file handle
    lea  rdx, msg                  ; RDX (arg 2) - address of begining of msg
    mov  r8, lengthof msg          ; R8  (arg 3) - msg length in bytes to terminating 0
    lea  r9, nBytesWritten         ; R9  (arg 4) - address of variable to write result to
    call WriteConsoleA             ; call the function (no return)

    ; restore the console text attributes
    ; void SetConsoleTextAttribute(RCX, RDX)
    mov  rcx, stdout              ; RCX (arg 1) - file handle 
    mov  rdx, 07h                 ; RDX (arg 2) - bgcolor = 0x0 (Black), fgcolor = 0x7 (Grey)
    call SetConsoleTextAttribute  ;

    ; clean up and exit
    add  rbp, 40                   ; release the 40-bytes from the stack
    mov  rax, nBytesWritten        ; set the return code to number of bytes written
    mov  rcx, 0                    ; set the exit code 0
    call ExitProcess               ; Jump to ExitProcess function
main endp

end