Question $4(9\mathrm{.}23$ textbook page $355)$

The starting address of the trap routine is stored at the address specified in the TRAP instruction. IVhy isn't the first instruction of the trap routine stored at that address instead? Assume each trap service routine requires at most $16$ instructions. Modify the semantics of the LC$-3$ TRAP instruction so that the trap vector provides the starting address of the service routine.