(Interrupt ReQuest line) A hardware resource in your computer which enables an expansion card to interrupt your computer's CPU. Many expansion cards require their own IRQ line which is then unavailable to other expansion cards. Unfortunately, IBM-compatible personal computers require the user to allocate the available IRQ lines when installing an expansion card. This makes upgrading a personal computer harder than necessary. Someday a new technology called "Plug and Play" will automatically take care of this problem. If you physically changed the IRQ setting for a serial port to a nonstandard value, you must make a corresponding change in the Windows Control Panel.