noop

NOOP, short for "no operation" (also written no-op), is a term used in computing to denote an instruction or action that has no observable effect on the state of a system. In machine code and assembly language, a NOOP instruction does nothing beyond advancing the program counter and consuming a processor cycle. Many CPUs provide a dedicated NOOP opcode, while others implement a harmless instruction sequence that achieves the same result.

NOOPs are used for timing, alignment, or to reserve space for future patches. They can fill delay slots in pipelined processors, align instructions to boundaries for performance, or serve as placeholders when code is temporarily disabled.

In higher-level software, a NOOP can be a function or method that performs no action and returns immediately. No-op functions are common as default callbacks, stubs during development, or shims that preserve an interface while substituting alternative behavior. They help maintain compatibility, simplify testing, or allow runtime behavior changes without altering call sites.

The concept also appears in configuration and protocol design as a value or operation that signals "do nothing" when encountered, often used in command parsers and scripting environments.

Etymology and usage: originating in early computer science, the term NOOP is widely used across languages and architectures to denote a harmless operation. In practice, a NOOP is any operation that yields no observable effect beyond consuming time or cycles.