Hello world

; hello.asm
;
; $ xa hello.asm
; $ run6502 -l 600 a.o65 -R 600 -P 1000 -X 0
; Hello, world!
; $

putchar =   $1000
    *=  $600
start   ldx #$00
loop    lda msg,x
    beq stop
    jsr putchar
    inx
    jmp loop
msg .asc    "Hello, world!", 10, 0
stop    brk