Register

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It is still under construction and content may change. Do not rely on this information.

A register is a high-speed memory location within a CPU.

Various types of registers are used in combination in various computer architectures:

• General-purpose registers are used to temporarily store values.
• Accumulators hold the results of mathematical operations (originally add/subtracts, but now any numerical operation).
• Status registers (or Flag registers, or Condition code registers) contain flag bits, which are set/cleared/tested either explicitly (by instructions) or implicitly (as the result of other operations). For example, the ARM aarch32 "Z" flag is set ("1") if an operation has a non-zero result, and cleared ("0") if an operation has a non-zero result. This flag is one bit within the Application Processor Status Register (APSR).
• Control registers alter the operation of the processor, such as by enabling binary coded decimal (BCD) math or toggling little-endian/big-endian mode.

The term register may also be used to refer to an IO port or a memory address within a memory-mapped input/output device, used to set/read device status and parameters.