Processor register

A processor register is a small, fast storage location inside a processor that holds data, addresses, or control information during instruction execution. Registers are directly accessible to the processor and are distinct from main memory.

Instruction register: A processor register that holds the instruction currently being decoded or executed. It keeps the active instruction available while the processor interprets it.
Instruction set architecture: The programmer-visible specification of a processor's instructions, registers, data types, and memory behavior. It defines which registers software can name and how instructions may use them.
Accumulator architecture: A processor organization in which many operations implicitly use one special accumulator register. It contrasts with designs that expose several general-purpose registers as explicit operands.
Register allocation: A compiler process that assigns program values to a limited set of machine registers. It determines which values remain in fast registers and which must be spilled to memory.
Program counter: A processor register that identifies the address of the next instruction to fetch. It steers instruction execution by tracking where the next instruction resides.
Central processing unit: The electronic component that executes instructions and performs computation in a computer. Registers are storage elements within this instruction-executing component.
Stack machine: A processor architecture that performs operations mainly on values at the top of an implicit stack. It minimizes explicitly named registers by obtaining operands from stack positions.
Calling convention: Rules governing how software passes arguments, returns results, and preserves state across function calls. It specifies which registers functions may use freely and which they must preserve.
Status register: A processor register containing condition flags and other state used to control execution. Its flags record results that later instructions use for conditional behavior.
Addressing mode: A rule specifying how an instruction identifies the location of an operand. Some modes use register contents as addresses or combine them with offsets.

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