Boot Device

In computing, booting is the process of starting a computer as initiated via hardware such as a physical button on the computer or by a software command. 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. This may be done by hardware or firmware in the CPU, or by a separate processor in the computer system. On some systems, a power-on reset (POR) does not initiate booting, and the operator must initiate booting after POR completes. IBM uses the term Initial Program Load (IPL) on some product lines. Restarting a computer is also called rebooting, which can be hard, e.g., after electrical power to the CPU is switched from off to on, or soft, where the power is not cut. On some systems, a soft boot may optionally clear RAM to zero. Both hard and soft booting can be initiated by hardware, such as a button press, or by a software command. Booting is complete when the operative runtime system, typically the operating system and some applications, is attained. The process of returning a computer from a state of sleep (suspension) does not involve booting; however,