BOOTING IN COMPUTER
What is Booting ?
Booting in computer is defined as a region on the hard disk, floppy disk, optical disk (or) any other storage device used for storing the data. This region typically consists of the code that needs to be loaded by the firmware of the system onto the Random Access Memory (RAM). Thereby it serves the purpose of loading programs onto the storage device by utilizing the boot process of the same device.
What is the process BOOTING In Computer?
The booting of the PC is one of the major jobs accomplished by the BIOS. The booting process involves a sequence of complex steps that include verification of configuration, checking the hardware, and loading of software. The following are the typical steps carried out during the system boot sequence.
At first, the user turns ON the power switch of the PC, this initializes the internal power supply. But at this moment, the power supply is incapable of providing power to the entire PC. After a few seconds, the power supply becomes capable of distributing power to the motherboard in a form of a good power signal to the motherboard chipset. Now, the motherboard transmits the system reset command to the processor. A moment in time, from the user’s point of view the system appears as still it is powered off.
Upon sending the system reset command by the motherboard chipset, the CPU starts its process by reading the first instruction from the jump address. The location of the jump address is fixed which is typically FFFFOh in system memory. The jump address usually stores the physical address that corresponds to the BIOS boot program across the ROM BIOSchip.
After step-2, the first instruction is executed by the CPU. This copies BiOS programs into system memory and leads to the initialization of BIOS running.
In this step, the BIOS performs the verification and testing of hardware configuration by adopting a process called the post process (Power-on SelfTest). When the POST detects any problem, the system raises the beep codes. Multiple beeps through the system indicate the nature of the problem. Also, it displays error messages, which leads to the halting of the boot process.
In this step, when the boot POST process discovers that there are no errors, then it continues the boot process. After this, BIOS is booting the PC checks for the video adapter’s BIOS so as to start. All the peripheral devices connected to the PC are virtually considered to have their own BIOS. In new generation PCs, besides producing the noises of disk drives gives only it single beep sounds which indicate that the PC is booting. After this, the video card information is displayed on the screen.
Once, the information with respect to the video adapter is displayed on the screen, another information about the system BIOS is displayed, the system BIOS information is nothing but information about the manufacture and the version of the BIOS program.
In this step, as soon as the devices present on the system start its BIOS routines, then at that moment of time the video cards BIOS first initiates to turn ON the display. This is followed by the display of information on system BIOS and other BIOS respectively.
After this, the BIOS performs a series of tests on the System. These tests determine the total amount of memory 1dentified on the system, the obtained information to the est is displayed on the screen in the form of a run-up counter showcasing the amount of memory in the system. With the introduction of the monitors, the BIOS instead of raising any beep codes started displaying the error messages for any incurred problem.
In this step, the system BIOS performs analysis in order to see whether the devices present in the CMOS configuration data function properly. This includes their speeds, access modes, and another parameter. Here each serial port and parallel ports attain their identities such as COM1, COM2, LPTI, etc. And whenever the device is passed, the BIOS displays a message that the device was found, configured, and tested.
A plug-and-play technology (PnP) is supported by BIOS. So, each time a PnP device is detected, it is configured. The information related to each and every PnP device gets displayed on the screen but it just runs on the screen quickly making it difficult for the user to read it.
This step shows the end of the test and configuration sequences. The BIOS generates a summary data screen representing the details of the PC. This indicates that the system is verified and ready for use.
In this step, to run the operating system the BIOS first has to search it. For this purpose, a parameter is used present in CMOS data. The role of the parameter is to indicate the disk drives such as floppy, hard, or CD-ROM. It also shows the arrangement or form in which these disk drives are accessed so as to locate the operating system.
Mostly, the boot sequence parameters perform analysis by searching the operating system first on the floppy disk drive then the hard disk drive. But if it fails to find the OS it checks the CD-ROM drive. The sequence for the search can be altered making the first boot device be hard disk and the BIOS searches for the master boot record to start the operating system.