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BIOS interrupt calls perform hardware control or I/O functions requested by a program, return system information to the program, or do both. A key element of the purpose of BIOS calls is abstraction - the BIOS calls perform generally defined functions, and the specific details of how those functions are executed on the particular hardware of the system are encapsulated in the BIOS and hidden ...
A modern PC is configured to attempt to boot from various devices in a certain order. If a computer is not booting from the device desired, such as the floppy drive, the user may have to enter the BIOS Setup function by pressing a special key when the computer is first turned on (such as Delete, F1, F2, F10 or F12), and then changing the boot order. [6]
The BIOS uses the boot devices set in Nonvolatile BIOS memory , or, in the earliest PCs, DIP switches. The BIOS checks each device in order to see if it is bootable by attempting to load the first sector (boot sector). If the sector cannot be read, the BIOS proceeds to the next device.
Windows Recovery Environment (WinRE) is a set of tools based on Windows PE to help diagnose and recover from serious errors which may be preventing Windows from booting successfully. Windows RE is installed alongside Windows Vista and later, and may be booted from hard disks, optical media (such as an operating system installation disc) and PXE ...
A bootable MBR device is defined as one that can be read from, and where the last two bytes of the first sector contain the little-endian word AA55h, [nb 6] found as byte sequence 55h, AAh on disk (also known as the MBR boot signature), or where it is otherwise established that the code inside the sector is executable on x86 PCs.
With UEFI, it is possible to store product keys for operating systems such as Windows, on the UEFI firmware of the device. [21] [22] [23] UEFI is required for Secure Boot on devices shipping with Windows 8 [24] [25] and above. It is also possible for operating systems to access UEFI configuration data. [26]
Some virtual machine infrastructure can directly import and export a boot image for direct installation to "bare metal", i.e. a disk. This is the standard technique for OEMs to install identical copies of an operating system on many identical machines: The boot image is created as a virtual machine and then exported, or created on one disk and then copied via a boot image control ...
In these cases a computer can often be "redirected" to boot from a USB device through use of an initial bootable CD or floppy disk. [ 5 ] [ 6 ] [ 7 ] Some Intel-based Macintosh computers have limitations when booting from USB devices – while the Extensible Firmware Interface (EFI) firmware can recognize and boot from USB drives, it can do ...