MFILL    MAC
         _ISLIT ]1
         _ISLIT ]2
         LDA   ]3         
         PHA
         JSR   MEMFILL
         <<<
BEEP     MAC
         LUP   ]1
         JSR   BELL
         --^
         <<<
MMOVE    MAC
         _ISLIT ]1
         _ISLIT ]2
         _ISLIT ]3
         JSR   MEMMOVE
         <<<
DELAY    MAC
         LDY   ]1
         JSR   DELAYMS
         <<<
ZSAVE    MAC
         _ISLIT ]1
         JSR   ZMSAVE
         <<<
ZLOAD    MAC
         _ISLIT ]1
         JSR   ZMLOAD
         <<<
MSWAP    MAC
         _ISLIT ]2
         _ISLIT ]1
         LDA   ]3
         PHA
         JSR   MEMSWAP
         <<<