A flat fee, also referred to as a flat rate or a linear rate, refers to a pricing structure that charges a single fixed fee for a service, regardless of usage.[1] Less commonly, the term may refer to a rate that does not vary with usage or time of use.
Synchronous: interrupt occurs as a result of current process, otherwise asynchronous. User requested: interrupt occurs because of direct result by user task, otherwise coerced. Maskable: if desired the interrupt can be disabled by a user task, otherwise unmasked.
1 Included two timers, a DMA controller, and an interrupt controller on the chip in addition to the processor (these were at fixed addresses which differed from the IBM PC, although it was used by several PC compatible vendors such as Australian company Cleveland).