.db MAX_MEM 0xFFFF
.db VIDEO_MEM 0xF37F
;.db MAX_LENGTH MAX_MEM - MAX_LENGTH
.db MSG "Hello, World!", 0

_start:
    copy r1, MSG ; Pointer into r1
    copy r8, VIDEO_MEM
    call strlen
    copy r1, MSG
    cmp r2, 0
    jz _end
    cmp r2, MAX_LENGTH
    jg _end
draw_loop:
    copy byte [r8], [r1]
    inc r1
    inc r8
    dec r2
    cmp r2, 0
    jz _end
    jmp draw_loop
_end:
    jmp _end

; Returns the length of a NULL terminated string
; Arguments: R1 - Pointer to the string
; Returns: R2 - Contains the length of the string
strlen:
    copy r2, 0 ; length
    copy byte r4, [r1]
    cmp r3, 0
    jz end ;The string is zero length
loop:
    inc r1
    copy byte r3, [r1]
    cmp r3, 0
    jz end
    inc r2
    jmp loop
end:
    ret