Used by command lists 0x16, 0x18, 0x1C and 0x4E. Copies the address of the point reached in the current command list (stored in bytes 0x19 and 0x1A of the character's buffer) into bytes 0x1B and 0x1C (where the start address of the current command list is stored). This means that whenever the command list is restarted, it will restart from this point instead of the actual beginning.