Double precision addition, multiplication and division of binary numbers are briefly covered. The BIOS routines buffer the application program from the system resources to prevent user error or abuse. The resident monitor are the BIOS routines always in memory allocated to them. The typical way they are accessed is via a dispatch routine using vectored linking using a branch table of some sort. The main point about access control is the difference between supervisor mode and user mode.
Exceptions are error condiations.
They execute in supervisor mode, although it's not unusual to have user-supplied exception handlers. The exception mechanism can also be used to implement breakpoint debugging. See Figure 12.3. See Figure 12.4. The interaction of the application program called BIOS routines and the interrupt handlers is shown in Figures 12.3, 12.5, 12.9, and 12.10.