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Furthermore, on a modern x86 system, BIOS calls can only be performed in Real mode, or Virtual 8086 mode. v8086 is not an option in Long mode. This means that a modern operating system, which operates in Protected mode (32 bit), or Long mode (64 bit), would need to switch into real mode and back to call the BIOS - a hugely expensive operation.
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 ...
INT 16h, INT 0x16, INT 16H or INT 22 is shorthand for BIOS interrupt call 16hex, the 23rd interrupt vector in an x86-based computer system. The BIOS typically sets up a real mode interrupt handler at this vector that provides keyboard services. This interruption is responsible for control of the PC keyboard.
A Deferred Procedure Call (DPC) is a Microsoft Windows operating system mechanism which allows high-priority tasks (e.g. an interrupt handler) to defer required but lower-priority tasks for later execution. This permits device drivers and other low-level event consumers to perform the high-priority part of their processing quickly, and schedule ...
Ideally, only highly trusted kernel code is allowed to execute in the unrestricted mode; everything else (including non-supervisory portions of the operating system) runs in a restricted mode and must use a system call (via interrupt) to request the kernel perform on its behalf any operation that could damage or compromise the system, making it ...
INT is an x86 instruction that triggers a software interrupt, and 13 hex is the interrupt number (as a hexadecimal value) being called. Modern computers come with both BIOS INT 13h and UEFI functionality that provides the same services and more, with the exception of UEFI Class 3 that completely removes CSM thus lacks INT 13h and other interrupts.
In this example of dual booting, the user chooses by inserting or removing the DVD from the computer, but it is more common to choose which operating system to boot by selecting from a boot manager menu on the selected device, by using the computer keyboard to select from a BIOS or UEFI Boot Menu, or both; the Boot Menu is typically entered by ...
The first DPMI specification drafts were published in 1989 by Microsoft's Ralph Lipe. [4] [1] While based on a prototypical version of DPMI for Windows 3.0 in 386 enhanced mode, several features of this implementation were removed from the official specification, including a feature named MS-DOS Extensions [5] or DOS API translation that had been proposed by Ralph Lipe in the original drafts. [6]