Structure and role of the processor and its components key terms

General-purpose register

A processor register used as temporary storage for data or intermediate results during processing.

Dedicated register

A register assigned a specific role in processor operation, such as storing an instruction address, an instruction, a memory address or status information.

Fetch-Execute cycle

The repeated process in which the processor fetches a machine code instruction, decodes it and executes it.

Current instruction register

The register that holds the instruction currently being decoded or executed.

Processor instruction set

The set of instructions that a particular processor can interpret and execute.

Operand

The part of an instruction that provides a value, memory address or register for the operation.

Operand

The part of an instruction that supplies a datum or identifies the address of a datum, depending on the addressing mode.

Addressing mode

The way an instruction specifies or identifies the datum to be used.

Mnemonic

A human-readable abbreviation used to represent a machine-code operation in assembly language, such as LOAD, ADD or STORE.

Direct addressing

An addressing method in which the operand identifies the memory location containing the data to be used.

Interrupt

A request that causes the processor to temporarily divert from its current program so that it can deal with an event.

Interrupt service routine (ISR)

A routine executed by the processor to service an interrupt.

Word length

The number of bits that a processor can process as a single unit.

Cache memory

Fast memory located close to the processor that stores frequently or recently used instructions and data.