Halt

Halt is a verb meaning to bring to a stop or to cause something to stop moving, operating, or progressing. It can refer to physical motion, the continuation of a process, or the delay or suspension of an activity. As a noun, a halt is an interruption or stop in a sequence or operation.

In computing, halt denotes the termination of a program, process, or system. The halt command in Unix-like operating systems initiates the shutdown sequence and, depending on the hardware and configuration, may halt the CPU or power off the machine. Modern systems often implement shutdown and halt as coordinated actions within an init system (such as systemd) rather than as a standalone routine.

In computer architecture, a halt instruction or state stops the processor from executing further instructions. On many CPUs, a halt instruction (for example, the x86 HLT) stops the processor until an interrupt occurs; the processor may then resume operation. In other architectures, the processor enters a low-power idle state instead of a complete shutdown.

Beyond computing, halt is used in general English to describe the cessation of motion or progress, such as a halt in negotiations, a traffic halt, or a temporary halt in production. The term is also found in phrases that denote a pause or interruption in various activities or plans.