Software-generated exceptions fall into two categories:
Software exceptions generated as a result of an error condition detected while attempting execution of an instruction. The type of error condition defines the IDT entry that is vectored to.
Software exceptions deliberately generated by execution of special instruction types (e.g., INT and BOUND). Special exceptions are also generated by the INT nn, INTO, and INT3 instructions:
- Execution of an INT nn instruction vectors to entry nn in the IDT.
- Execution of an INTO instruction vectors to IDT entry four if EFlags[OF] = 1.
- Execution of the INT3 instruction (the breakpoint instruction) vectors to IDT entry three.
- Conditionally generated by the BOUND instruction ...