assembler format/syntax), implementing the classic "Hello, world!" program:

CHROUT = $ffd2 ; CHROUT is the address of the character output routine CR = $0d ; PETSCII code for Carriage Return ; hello: ldx #0 ; start with character 0 by loading 0 into the x index register next: lda message,x ; load byte from address message+x into the accumulator beq done ; if the accumulator holds zero, we're done and want to branch out of the loop jsr CHROUT ; call CHROUT to output char to current output device (defaults to screen) inx ; increment x to move to the next character bne next ; loop back while the last character is not zero (max string length 255 bytes) done: rts ; return from subroutine ; message: .byte "Hello, world!" .byte CR, 0 ; Carriage Return and zero marking end of string