Glossary 15
interface
A connection that enables two devices to communicate.
interrupt
A signal from part of a system, such as an I/O device, asking to
use the CPU. Interrupts are hierarchical, which prevents
interrupts from interrupting each other. (Whichever interrupt
has higher priority makes the other interrupt wait.) When the
CPU receives an interrupt signal, it saves what it is doing,
processes the routine associated with the interrupt, then returns
to what it was doing.
I/O address
Input-Output address. How the CPU sees an I/O port. It puts
data into this address or reads the data in it. The device at the
other end of the I/O port gets the data from that address or puts
the data there, respectively.
IRQ
Interrupt Request. A signal that, when received by the CPU,
makes it stop what it is doing to do something else. An
interrupt is a way in which a particular device in a computer
communicates with the CPU. PCs have 16 IRQ lines that can
be assigned to different devices (for example, printers,
scanners, modems). No two devices can have the same IRQ
address. See interrupt.
