Explanation:

The question asks for the term used when a computer, already powered on, is restarted. This process involves the operating system initiating a reboot without completely cutting power to the system. Option (c) 'Warm booting' accurately describes this scenario. Warm booting is typically performed when the system is running, for example, by selecting 'Restart' from the operating system menu. Option (a) 'Shut down' refers to turning off the computer completely. Option (b) 'Cold booting' refers to starting a computer from a completely powered-off state. Option (d) 'Logging off' means ending a user session while the computer remains on and potentially other users can log in. Therefore, 'Warm booting' is the precise term for restarting an already running computer.