In computing, booting (or booting up) is the initialization of a computerized system. The system can be a computer or a computer appliance. The booting process can be "hard", after electrical power to the CPU is switched from off to on (in order to diagnose particular hardware errors), or "soft", when those power-on self-tests (POST) can be avoided. Soft booting can be initiated by hardware such as a button press, or by software command. Booting is complete when the normal, operative, runtime environment is attained.