In computing, rebooting is the process by which a running computer system is restarted, either intentionally or unintentionally. Reboots can be either cold (alternatively known as hard) whereby the power to the system is physically turned off and back on again, causing an initial boot of the machine, or warm (alternatively known as soft) where the system restarts without the need to interrupt the power. The term restart is used to refer to a reboot when the operating system closes all programs and finalizes all pending input and output operations before initiating a soft reboot. Early electronic computers (like the 1401) had no operating system and little internal memory. The input was often a stack of punch cards. The computer was initiated by pressing a start button that performed a single command, read a card. This first card then instructed the machine to read more cards that eventually loaded a user program. This process was likened to an old saying, “picking yourself up by the bootstraps”, referring to a horseman who lifts himself off the ground by pulling on the straps of his boots. This set of initiating punch cards was called “bootstrap cards”. Thus a cold start was called booting the computer up. If the computer crashed, it was rebooted. The boot reference carried over to all subsequent types of computers. For more, see Bootstrapping.