.code16
.global _start

.equ STACK_SEGMENT, 0x8E00
.equ ORG_SEGMENT, 0x0

.text
_start:
        cli
        jmp $ORG_SEGMENT, $(asmain)

asmain:

        xor %ax, %ax
        mov %ax, %ds
        mov %ax, %es
        mov %ax, %ss

        mov $STACK_SEGMENT, %sp

        mov $0xDEAD, %ax # Print a determined value to check if the function
                         # itself is working.
        call printRegister
        call putSeparator

        mov $msg, %ax # FIXME
        call printRegister # Nothing is printed; the '.' is never printed.


.end:
        mov $'.', %al
        call printChar

.stop:
        cli
        hlt
        jmp .stop

printChar:
        # print char in %Al

        mov $0xE, %ah # interrupt service
        mov $0x3, %bh # BH = page number = 0 ; BL = 3 = Cyan (ignored)
        pusha # BIOS might be nasty
        int $0x10
        popa

        ret

putSeparator:
        mov $'_', %al
        call printChar
        ret

printRegister:

        test %ax, %ax # test for 0, that would
        jne .go
        mov $'0', %al
        call printChar
        ret

.go:
        mov $10, %bx
        xor %cx, %cx # number of elements pushed.
        xor %dx, %dx # high part of dividend
.loop:
        div %bx     # result = %AX ; remaineder = %DX

        # we're not done yet:
        # Increment n. of elements
        add $1, %cx  # elements to show

        add $0x30, %dx # convert to ASCII
        push %dx

        test %ax, %ax # should we continue?
        je .show

        # Prepare %AX for next divs.
        xor %dx, %dx
        jmp .loop

.show:
        pop %dx

        mov %dl, %al # load character -- already printable
        call printChar

        sub $1, %cx
        test %cx, %cx
        jnz .show

        ret

msg: .asciz "You shall not see this message on real hardware."

.space 510 - (. - _start)
.word 0xaa55