.386
.model flat, stdcall

includelib <c:masm32libkernel32.lib>
includelib <c:masm32libuser32.lib>

ExitProcess PROTO , :DWORD
MessageBoxA PROTO , :DWORD, :DWORD, :DWORD, :DWORD

.data
caption db "MyPr", 0
message db "to be or not to be. there is the question.", 0

.code
Winmain PROC
    lea esi, message

_proc:
    mov al, [esi]

    cmp al, 0
    jz _end

    cmp al, 'a'
    jna _next

    cmp al, 'z'
    jnb _next

    add BYTE PTR [esi], 'A' - 'a'

_next:
    inc esi
    jmp _proc


_end:
    push 0
    push offset caption
    push offset message
    push 0
    call MessageBoxA

    push 0
    call ExitProcess

Winmain endp
end Winmain