When any type of interrupt is received, the [[Register#Program Counter|program counter ]] is typically pushed on the [[Stack|stack]], and then the program counter is loaded from an ''interrupt vector'' stored in a register or a pre-defined memory location, usually at the top of or bottom of physical [[Address|address space]]. Effectively, this means that a subroutine jump is performed to the interrupt-handling routine. In systems where multiple devices are connected to one hardware interrupt line, it is necessary to poll the PIC/APIC or the attached devices to determine which one(s) triggered the interrupt before servicing the request(s).