GATE CS 1995 Q1.3 — I/O Interface: Interrupt and DMA Mode

In a computer system, interrupts are classified based on how the processor determines the starting address of the Interrupt Service Routine (ISR):

• Vectored Interrupts: The interrupting device (source) supplies the branch information (an interrupt vector or vector address) to the processor, typically during the interrupt acknowledgment cycle. The processor then uses this vector to locate the starting address of the ISR from the interrupt vector table.
• Non-Vectored Interrupts: The branch address is fixed and pre-determined by the processor's hardware architecture. The processor always branches to this fixed memory location whenever that specific interrupt occurs.

Thus, in a vectored interrupt, the interrupting source supplies the branch information to the processor through an interrupt vector.