INT 10h, INT 10H or INT 16 is shorthand for

BIOS interrupt call BIOS interrupt calls are a facility that operating systems and application programs use to invoke the facilities of the Basic Input/Output System firmware on IBM PC compatible computers. Traditionally, BIOS calls are mainly used by DOS programs ...

10_hex, the 17th

interrupt vector An interrupt vector table (IVT) is a data structure that associates a list of interrupt handlers with a list of interrupt requests in a table of interrupt vectors. Each entry of the interrupt vector table, called an interrupt vector, is the addre ...

in an

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was intr ...

-based computer system. The BIOS typically sets up a real mode

interrupt handler In computer systems programming, an interrupt handler, also known as an interrupt service routine or ISR, is a special block of code associated with a specific interrupt condition. Interrupt handlers are initiated by hardware interrupts, softw ...

at this vector that provides video services. Such services include setting the video mode, character and string output, and graphics primitives (reading and writing

pixels In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the sm ...

in graphics mode). To use this call, load AH with the number of the desired subfunction, load other required parameters in other registers, and make the call. INT 10h is fairly slow, so many programs bypass this BIOS routine and access the display hardware directly. Setting the video mode, which is done infrequently, can be accomplished by using the BIOS, while drawing graphics on the screen in a game needs to be done quickly, so direct access to video RAM is more appropriate than making a BIOS call for every pixel. Furthermore, on a modern x86 system, BIOS calls can only be performed in Real mode, or

Virtual 8086 mode In the 80386 microprocessor and later, virtual 8086 mode (also called virtual real mode, V86-mode, or VM86) allows the execution of real mode applications that are incapable of running directly in protected mode while the processor is running a ...

. 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. Although most modern systems typically use device drivers that directly set the video mode, it is not feasible for hobbyist systems to have a device driver for every video card - a problem that also plagues older, unsupported systems such as

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. The second operating system in the 9x line, it is the successor to Windows 95, and was released to ...

. Such systems instead can drop into Real mode to switch the video mode, then draw to the framebuffer directly. In EFI 1.x systems, the INT 10H and the

VESA BIOS Extensions VESA BIOS Extensions (VBE) is a VESA standard, currently at version 3, that defines the interface that can be used by software to access compliant video boards at high resolutions and bit depths. This is opposed to the "traditional" int 10h BI ...

(VBE) are replaced by the EFI UGA protocol. In widely used

UEFI UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples of ...

2.x systems, the INT 10H and the VBE are replaced by the

UEFI GOP UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples ...

List of supported functions

''The list is incomplete; use Ralf Brown's list for comprehensive information. Please only add IBM/PC or other common standard functions. 00h through 0fh are CGA.''

References

INT 10h from Ralf Brown's Interrupt List, online version

INT 10h on www.ousob.com
{{DEFAULTSORT:Int 10h BIOS Interrupts

List of supported functions

See also

References