"hello, world" in 6502 Assembly Language for the Atari 2600 (Code Example from "Making Games for the Atari 2600" by Steven Hugg)

helloworld.a

        processor 6502

        include "vcs.h"
        include "macro.h"

        seg Code	
        org $f000	; start code at $f000

Start   sei             ; disable interrupts
        cld             ; disable BCD math mode
        ldx #$ff        ; init stack pointer to $FF
        txs             ; transfer X register to S register
        
        lda #0          ; set A register to zero
        ldx #$ff        ; set X to #$ff
ZeroZP	sta $0,X        ; store A register at address ($0 + X)
        dex             ; decrement X by one
        bne ZeroZP      ; branch until X is zero
        
        ; Make Background Red
        lda #$30        ; load value into A ($30 is deep red)
        sta COLUBK	; store A into background color register
        
        jmp Start	; goto start of program
        
        org $fffc
        .word Start	; reset vector at $fffc
        .word Start	; interrupt vector at $fffe (unused in VCS)