vectortable

A vectortable, also known as an interrupt vector table or dispatch table, is a data structure used in computer systems to manage interrupts. It typically consists of an array of memory addresses. Each entry in the table corresponds to a specific interrupt or exception event. When an interrupt occurs, the processor uses the interrupt number as an index into the vectortable to find the memory address of the interrupt handler routine. This routine is a piece of code specifically designed to deal with that particular interrupt.

The vectortable is usually located at a fixed memory address, often at the beginning of the system's memory. This fixed location allows the processor to quickly locate the table without needing to search for it. In many systems, the operating system is responsible for initializing the vectortable during the boot process, populating it with the correct addresses of the interrupt service routines (ISRs).

When an interrupt is triggered, the processor suspends its current execution, saves its current state (like the program counter and processor flags), and then jumps to the address specified in the vectortable for that interrupt. After the interrupt handler finishes its task, it typically restores the saved processor state and resumes the interrupted program from where it left off. This mechanism is crucial for handling events like hardware interrupts (e.g., keyboard input, disk I/O), software interrupts (e.g., system calls), and exceptions (e.g., division by zero, memory access violations).