To store data, you have to have a label. stuff: .db $00,$00,$0F to access that data, use this: ld hl,PROGRAM_ADDR ;gets start of program, stored by ZS ld de,stuff ;takes the label offset add hl,de ;hl now contains the address of the first byte to load numbers to that location: ld (hl),a ;would load a into the first byte after stuff: Again, use this somewhere in your code: ld hl,ZS_BITS set 0,(hl) Enjoy, Alan B.