Switches and cables used to program ENIAC (1946) Growth in the capacity of ROM has allowed ever more elaborate start up procedures to be implemented. The invention of read-only memory (ROM) of various types solved this paradox by allowing computers to be shipped with a start up program that could not be erased. Early computers used a variety of ad-hoc methods to get a small program into memory to solve this problem. The usage calls attention to the requirement that, if most software is loaded onto a computer by other software already running on the computer, some mechanism must exist to load the initial software onto the computer. In addition to loading an operating system or stand-alone utility, the boot process can also load a storage dump program for diagnosing problems in an operating system.īoot is short for bootstrap or bootstrap load and derives from the phrase to pull oneself up by one's bootstraps. All computing systems are state machines, and a reboot may be the only method to return to a designated zero-state from an unintended, locked state. Minimally, some embedded systems do not require a noticeable boot sequence to begin functioning and when turned on may simply run operational programs that are stored in ROM. The process of returning a computer from a state of sleep (suspension) does not involve booting however, restoring it from a state of hibernation does. Booting is complete when the operative runtime system, typically the operating system and some applications, is attained. Both hard and soft booting can be initiated by hardware such as a button press or by a software command. On some systems, a soft boot may optionally clear RAM to zero. after electrical power to the CPU is switched from off to on, or "soft", where the power is not cut. Restarting a computer also is called rebooting, which can be "hard", e.g. This may be done by hardware or firmware in the CPU, or by a separate processor in the computer system. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some process must load software into memory before it can be executed. In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command.
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