C64_SKILLS/examples/assembly/safe-vic-bit-set.asm

; safe-vic-bit-set.asm
; Demonstrates read-modify-write for VIC-II registers.
; Enables sprite 0 without changing other sprite-enable bits.

        * = $c000

start:  lda $d015      ; VIC-II sprite enable
        ora #$01       ; set bit 0
        sta $d015
        rts