The process of starting or restarting a computer system by loading instructions
Introduction¶Booting is a startup sequence that starts the operating system of a computer when it is turned on. A boot sequence is the initial set of operations that the computer performs when it is switched on. Every computer has a boot sequence. The average computer doesn’t understand the boot sequence but is important to know for customizing and troubleshooting your computer. Boot Loader¶Computers powered by the central processing unit can only execute code found in the systems memory. Modern operating systems and application program code and data are stored on nonvolatile memories or mass storage devices. When a computer is first powered on, it must initially rely only on the code and data stored in nonvolatile portions of the systems memory. At boot time, the operating system is not really loaded and the computer’s hardware cannot peform many complex systems actions. The program that starts the “chain reaction” which ends with the entire operating system being loaded is known as the boot loader (or bootstrap loader). The term creatively came from early designiners imagining that before a computer “runs” it must have it’s “boots strapped”. The boot loader’s only job is to load other software for the operating system to start. Often, multiple-stage boot loaders are used, in which several small programs of increasing complexity sequentially summon one after the other, until the last of them loads the operating system. Boot Devices¶The boot device is the device from which the operating system is loaded. A modern PC BIOS (Basic Input/Output System) supports booting from various devices. These include the local hard disk drive, optical drive, floppy drive, a network interface card, and a USB device. Typically, the BIOS will allow the user to configure a boot order. If the boot order is set to:
then the BIOS will try to boot from the CD drive first, and if that fails then it will try to boot from the hard disk drive, and if that fails then it will try to boot from the network, and if that fails then it won’t boot at all. Boot Sequence¶There is a standard boot sequence that all personal computers use. First, the CPU runs an instruction in memory for the BIOS. That instruction contains a jump instruction that transfers to the BIOS start-up program. This program runs a power-on self test (POST) to check that devices the computer will rely on are functioning properly. Then, the BIOS goes through the configured boot sequence until it finds a device that is bootable. Once BIOS has found a bootable device, BIOS loads the bootsector and transfers execution to the boot sector. If the boot device is a hard drive, it will be a master boot record (MBR). The MBR code checks the partition table for an active partition. If one is found, the MBR code loads that partition’s boot sector and executes it. The boot sector is often operating system specific, however in most operating systems its main function is to load and execute the operating system kernel, which continues startup. If there is no active partition or the active parition’s boot sector is invalid, the MBR may load a secondary boot loader which will select a partition and load its boot boot secotr, which usually loads the corresponding operating system kernel. Exercises¶7 Answers First step: When we press the power switch, the supply will start to the mainboard and other equipment, power, voltage stability, not too on the mainboard chipset to CPU control will be issued and maintain a RESET (RESET) signal, let the CPU automatically restored to its
original state within the CPU at this moment, but not immediately executes instructions. Booting is the term used to start up a computer from an unpowered or uninitialized state. The term comes from the idea that "a cowboy would have to pick himself up by his bootstraps," which is really an impossible task. But if you consider that a computer doesn't even know how to communicate with its own hard drive when it's first turned on, there is a similar dilemma. It needs an operating system to operate, but the operating system IS on the hard drive. So to solve this dilemma, some computer commands that are needed to start up are hard coded into memory on a chip called the Boot ROM in the BIOS. So when we say we need to 'reboot' or 'cold boot,' what we are saying is to restart the computer all the way from zero. It will reload the entire operating system and initialize all hardware components so you have a usable computer. A 'soft start' is when only part of the system is restarted. The original term for Boot was Initial Program Load or IPL. And Boot is an abbreviation for Bootstrap. When you initially power on a computer, there is no Operating System Software in memory. This creates a Catch-22. Without software in memory, how can you load software into memory? You need to Boot or IPL. There are enough instructions and info in the Firmware or microcode of a computer to do the IPL. And it's much less volitale than instructions on a hard drive and it is operating system independent. On a PC, it's called the BIOS. One of the items in the BIOS is the drive letter of the IPL device. This allows you to change the device during the IPL process in case the default device is corrupted. The only remaining item to be determined is the location of the software on the device. The Bios does not have access to a directory or the instructions necessary to find the IPL instructions on the device. Therefore, the location is by convention, Sector zero(I believe?) on a PC is the location of the IPL instructions. Once the IPL instructions are loaded into memory, the processor can use them to load the actual Operating System Software. At that point, the full operating system software usually takes control. I state "usually" because of the way the windows operating system takes control. Because PCs have an unusually broad and complex array of hardware, as such, it requires specific software(drivers) to operate the devices. This can impact the initial operation of the software. To minimize the impact of those devices on the initial operation, windows can be loaded in "Safe Mode" to minimize the impact. This "Safe Mode" loads drivers that are common to a type of device and not vendor supplied. Booting is simply the loading the resources in operating system before starting the compute...... Starting up your computer of a program on you computer. Mainly it is the act of starting the hard drive and powering up the computer. Booting in computer is powering it on starting the operating system.which section will identify the performance is the boot process. Booting is the process of turning on the computer Answer Question |
