BOOTING AND REBOOTING

BOOTING

In computing, booting is the initial set of operations that a computer system performs when electrical power to the CPU is switched on. The process begins when a computer is turned on for the first time or is re-energized after being turned off, and ends when the computer is ready to perform its normal operations. On modern general purpose computers, this can take several seconds and typically involves performing a power-on self-test, locating and initializing peripheral devices, and then finding, loading and starting an operating system. Many computer systems also allow these operations to be initiated by a software command without cycling power, in what is known as a soft reboot, though some of the initial operations might be skipped on a soft reboot. A boot loader is a computer program that loads the main operating system or runtime environment for the computer after completion of the self-tests. When we start our computer then there is an operation which is performed automatically by the computer which is also called Booting. In Booting, the system will check all the hardware’s and software’s that are installed or attached with the system and will also load all the files needed for running a system.

In the booting process all the files that are stored into the ROM chip will also be loaded for running the system. In the booting process, the system will read all the information from the files that are stored into the ROM chip and the ROM chip will read all the instructions that are stored into these files. After the booting of the system this will automatically display all the information on the system. The Instructions that are necessary to start the system will be read at the Time of Booting.

TYPES OF BOOTING

1. Warm Booting: Warm booting refers to restarting a computer that is already turned on via the operating system. Restarting it returns the computer to its initial state. A warm boot is sometimes necessary when a program encounters an error from which it cannot recover. On PCs, you can perform a warm boot by pressing the Control, Alt, and Delete keys simultaneously. On Macs, you can perform a warm boot by pressing the Restart button. When the system starts from the starting point or from initial state. This is called as warm Booting. In the warm booting the system will be started from its beginning. This means first of all, the user will press the power button, then this will read all the instructions from the ROM and the Operating System will automatically gets loaded into the System.
2. Cold Booting: The start-up of a computer from a powered-down, or off state. The cold booting is that in which the system automatically starts when we are running the system. A cold boot, also called a cold start or hard boot, is a method of starting a computer in which the machine begins powering down or a specific function is sent to the computer’s processor that triggers a restart. In a normal cold boot process, the computer executes a small program. This process triggers another program to start, which loads the operating system.

REBOOTING

Rebooting is the process by which a running computer system is restarted, either intentionally or unintentionally. Reboots can be either hard (alternatively known as cold) whereby the power to the system is physically turned off and on again, causing an initial boot of the machine, or soft (alternatively known as warm) 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.

1. Hard Reboot: A hard reboot (also known as a cold reboot, or cold start) involves power cycling a computer or otherwise forcibly resetting the state of its hardware. A hard reboot may be commenced by disconnecting a power cord or battery, toggling a hardware power switch or pressing a dedicated reset button. A hard reboot may be caused by power failure, by accident or deliberately as a last resort to reset an unresponsive system or in case of a critical error.
2. Soft Reboot: A soft reboot (also known as a warm reboot) involves restarting a computer “normally” under software control, without power cycling the machine or (directly) triggering a hardware-based reset. It is usually, though not always, refers to an orderly shutdown and restart of the machine that includes safely flushing of any cached write operations to persistent storage. On some machines, the BIOS may perform a shorter initialisation sequence than it would for a cold start, for example by skipping steps such a power-on self-test or wiping sensitive information from the memory. The Control-Alt-Delete combination initiated a warm reboot on many legacy operating systems, including DOS and Windows 95. This key sequence was subsequently replaced on later operating systems, for example on Windows NT, where it has now become a secure attention sequence.