Boot Sector and BIOS


Hard drive
Boot sector and BIOS

The computer boot sector is the first sector of a computer's hard disk. The boot sector is where the computer loads the operating system.


The first computer boot sector was created in the early days of computing when operating systems were still stored on floppy disks. This boot sector was responsible for loading the operating system from the disk into memory so that it could be run on the computer.


With the advent of hard drives, the boot sector moved from the floppy disk to the hard drive, where it is still used today to load the operating system.


The boot sector is a small piece of code that is stored at the beginning of the hard drive, and it is responsible for loading the operating system into memory.


The boot sector is located at sector 0 of a disk and it is 512 bytes in size.



Types of boot sectors


There are three types of boot sectors:

  1. Master boot record (MBR)

  2. Extended boot record (EBR)

  3. Volume boot record (VBR)


Master boot record. The MBR is the first sector on a hard drive. The MBR contains the boot code that starts the boot process, and it also contains the partition table. The MBR is created when you create the first partition on a hard drive.


Extended boot record. The EBR is the second sector on a hard drive. The EBR contains the boot code that starts the boot process, and it also contains the partition table. The EBR is created when you create the second partition on a hard drive.


Volume boot record. The VBR is the third sector on a hard drive. The VBR contains the boot code that starts the boot process, and it also contains the partition table. The VBR is created when you create the third partition on a hard drive.


The boot sector is also responsible for loading the computer's BIOS.



BIOS


BIOS is an acronym for Basic Input/Output System. BIOS is a set of instructions that helps your computer talk to the different pieces of hardware in your computer. When you turn on your computer, the BIOS is the first thing that starts running. BIOS is responsible for starting your computer's operating system. It also helps your computer talk to your hardware, such as your hard drive, your graphics card, and your keyboard. BIOS is a very important part of your computer, and you should never change it unless you know what you're doing. If you change your BIOS settings incorrectly, you could damage your computer.



History of BIOS


The original IBM PC, XT, and AT all used a BIOS, which was a firmware program that provided the basic low-level functionality needed to start up the computer and load the operating system. The BIOS was stored in a read-only memory (ROM) chip on the motherboard. The IBM PC/XT used a ROM-based BIOS. The IBM AT used a flash-based BIOS. The IBM PC/XT used a ROM-based BIOS. The IBM AT used a flash-based BIOS.


In the early 1990s, IBM released the IBM PS/2 line of personal computers. The PS/2 used a new type of BIOS, called the Extensible Firmware Interface (EFI). EFI was more advanced than the traditional BIOS and provided many new features. However, EFI was not backward compatible with the BIOS, so it could not be used on older computers.


In the late 1990s, Intel released the first version of the x86-based Itanium processor. The Itanium used a new type of BIOS, called the Unified Extensible Firmware Interface (UEFI). UEFI was more advanced than the traditional BIOS and provided many new features. However, UEFI was not backward compatible with the BIOS, so it could not be used on older computers.


In the early 2000s, Intel released the first version of the x86-based Centrino processor that used UEFI.


In the mid-2000s, Microsoft released Windows Vista, which was the first version of Windows to support UEFI. Microsoft also released a new version of the Windows Boot Manager, called the Windows Boot Manager (WBM). The WBM was a replacement for the traditional BIOS, and provided many new features.


In the late 2000s, Intel released the first version of the x86-based Atom processor that used UEFI.


In the early 2010s, Intel released the first version of the x86-based Sandy Bridge processor that used UEFI.


In the late 2010s, Intel released the first version of the x86-based Skylake processor that used UEFI.



GUID Partition Table


GUID Partition Table (GPT) is a standard for the layout of the partition table on a physical storage device using a GUID, such as a hard disk drive or solid-state drive, to identify the partitions.


GPT is a replacement for the Master Boot Record (MBR) partitioning scheme, which uses 32-bit identifiers for partitions. In contrast, GPT uses 64-bit identifiers. This allows a much larger number of partitions (up to 128), and more importantly, more partitions can be smaller than 2 TiB in size, which is the limit for MBR partitions.


GPT also provides a facility for declaring partition types, which is used by operating systems to determine how to handle a partition. GPT is defined in the "Extensible Firmware Interface" (EFI) specification, version 2.3.1, published in 2005.



Types of boot sector viruses


There are three types of boot sector viruses:

  1. Master Boot Record viruses

  2. Boot sector viruses

  3. File infector viruses


Master Boot Record viruses are the most common type of boot sector virus. They infect the Master Boot Record, which is the first sector on a hard drive. This sector contains information about the drive's layout and is used by the computer to start up. Master Boot Record viruses can infect any type of hard drive, including floppy disks, CD-ROMs, and USB drives.


Boot sector viruses are less common than Master Boot Record viruses. They infect the boot sector, which is the first sector on a floppy disk or hard drive. The boot sector contains information about how the disk is formatted and how the files are organized. Boot sector viruses can only infect floppy disks and hard drives.


File infector viruses are the least common type of boot sector virus. They infect executable files, which are files that the computer can run. File infector viruses can infect any type of file, including floppy disks, CD-ROMs, and USB drives.



BIOS viruses


A BIOS virus is a type of computer virus that infects the BIOS of a computer system. BIOS viruses are typically spread through infected floppy disks, but can also be spread through other media, such as CD-ROMs and USB flash drives.


Once the BIOS is infected, the virus can spread to other parts of the computer system, including the hard drive and other storage devices.


BIOS viruses are not as common as other types of computer viruses, but they can be very dangerous, as they can be very difficult to remove.


To protect your computer from viruses you may want to use anti-virus software, be careful about what websites you visit and what files you download, and keep your computer's operating system up to date.