What is the IVT/IDT?
IVT stands for Interrupt Vector Table, and IDT stands for Interrupt Descriptor Table. The IVT is used in real-mode and the IDT is used in protected-mode. As the only time you should ever touch the IDT is if you are writing an OS from scratch, it won’t be discussed here. However, it’s the same idea conceptually. The IVT is located at address 0000:0000 in real-mode (note: it can be moved starting with the 80386, but that’s rare). The IVT is the mapping of interrupt numbers to interrupt handlers. In effect and actuality, it’s simply a jump table. Each four bytes corresponds to the address of a function.
