So, I decided to see what I would need to do to create a Windows program in assembly. Started with a basic Hello World example that I found on the internet, and then had to debug it to get it to compile and link correctly in MASM. Had to change title to win_title, for one of the ‘variables’, as title seems to be a reserved word. Went ahead and changed msg to win_msg to have a matching naming convention for both values.
;---ASM Hello World Win64 MessageBox
extrn MessageBoxA: PROC
extrn ExitProcess: PROC
.data
win_title db 'Hello', 0
win_msg db 'Hello World!', 0
.code
main proc
sub rsp, 28h
mov rcx, 0 ; hWnd = HWND_DESKTOP
lea r8, win_title ; LPCSTR lpCaption
lea rdx, win_msg ; LPCSTR lpText
mov r9d, 0 ; uType = MB_OK
call MessageBoxA
add rsp, 28h
mov ecx, eax ; uExitCode = MessageBox(...)
call ExitProcess
main endp
EndCode language: Intel x86 Assembly (x86asm)