Utility routines: ZERO

       Name: ZERO                                                    [Show more]
       Type: Subroutine
   Category: Utility routines
    Summary: Reset the local bubble of universe and ship status
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * RES2 calls ZERO
             * RESET calls ZERO


 This resets the following workspaces to zero:

   * UP workspace variables from FRIN to de, which include the ship slots for
     the local bubble of universe, and various flight and ship status variables


.ZERO

 LDX #(de-FRIN)         ; We're going to zero the UP workspace variables from
                        ; FRIN to de, so set a counter in X for the correct
                        ; number of bytes

 LDA #0                 ; Set A = 0 so we can zero the variables

.ZEL2

 STA FRIN,X             ; Zero the X-th byte of FRIN to de

 DEX                    ; Decrement the loop counter

 BPL ZEL2               ; Loop back to zero the next variable until we have done
                        ; them all

 RTS                    ; Return from the subroutine