Anyone who has ever tried to install a legacy (non plug-and-play) device has learned that device configuration can be a world of confusion. Fortunately, the entire concept of device configuration can be simplified by understanding three basic types of hardware resources: Interrupt Request (IRQ) Line Assignments, Direct Memory Access (DMA) Assignments, and memory locations known as Input/Output (I/O) Addresses. In this first one of three excellent articles, PC911 discusses IRQs with the intent of clarifying device configuration and resource conflict resolution.