this routine manages all system vector jump addresses stored in RAM. Calling this routine with the carry bit set will store the current contents of the RAM vectors in a list pointed to by the X and Y registers. When this routine is called with the carry bit clear, the user list pointed to by the X and Y registers is copied to the system RAM vectors. NOTE: This routine requires caution in its use. The best way to use it is to first read the entire vector contents into the user area, alter the desired vectors and then copy the contents back to the system vectors.