BIOS Interrupt Vector Table
BIOS Interrupt Vector Table

Introduction to BIOS Interrupt Vector Table

The BIOS Interrupt Vector Table, often abbreviated as IVT, is a fundamental component of low-level system programming that plays a crucial role in the interaction between software and hardware. It serves as a pivotal link in the chain of events when a hardware interrupt occurs in a computer system.

The BIOS IVT is a data structure located in the computer’s memory that contains a list of interrupt handlers. These interrupt handlers are small sections of code that are executed when a specific hardware interrupt occurs. Each interrupt handler is associated with a specific interrupt number, which is used to identify the type of interrupt that occurred.

The structure of the BIOS IVT is typically organized as an array, with each element representing a specific interrupt number. When an interrupt occurs, the computer looks up the corresponding interrupt handler in the IVT and transfers control to that section of code.

The purpose of the BIOS IVT is to provide a standardized interface for handling hardware interrupts. By using the IVT, software developers can write code that is independent of the specific hardware configuration of a computer system. This allows for greater portability and compatibility of software across different systems.

In summary, the BIOS Interrupt Vector Table is a crucial component of low-level system programming that facilitates the handling of hardware interrupts. Understanding its structure, purpose, and significance is essential for developers working with low-level programming and system-level software.

Interrupt handling in BIOS

Interrupt handling is a critical aspect of system responsiveness and stability in computer systems. Within the BIOS (Basic Input/Output System), interrupt handling plays a crucial role in managing both hardware and software interrupts, ensuring smooth operations and timely responses.

Hardware interrupts are signals generated by various hardware devices to request attention from the CPU. These interrupts can be triggered by events such as keyboard input, mouse movements, or disk operations. When a hardware interrupt occurs, the BIOS intercepts it and transfers control to the appropriate interrupt handler in the BIOS Interrupt Vector Table (IVT).

Software interrupts, on the other hand, are generated by software programs to request specific services from the BIOS. These interrupts are typically used for tasks such as disk operations, timekeeping, or accessing system resources. The BIOS handles software interrupts by transferring control to the corresponding interrupt handler in the IVT.

The BIOS IVT contains a list of interrupt handlers, each associated with a specific interrupt number. When an interrupt occurs, the BIOS looks up the corresponding interrupt handler in the IVT and transfers control to that section of code. The interrupt handler then performs the necessary operations to handle the interrupt and return control to the interrupted program.

By effectively managing interrupts, the BIOS ensures that hardware events are handled promptly and that software programs can access the necessary system services. This allows for efficient and reliable operation of computer systems.

In the next section, we will explore the structure and organization of the BIOS Interrupt Vector Table in more detail.

BIOS interrupt vector list

The BIOS Interrupt Vector List (IVT) is a crucial element in system programming, serving as a bridge between software and hardware by utilizing a set of interrupt handlers. This section will delve into the BIOS Interrupt Vector List, offering a comprehensive exploration of its structure, purpose, and its importance in the realm of low-level system programming.

The IVT is essentially a table that resides in the system’s memory, containing a list of interrupt handlers. Each interrupt handler is associated with a specific interrupt number, which corresponds to a particular hardware or software event. When an interrupt occurs, the BIOS consults the IVT to locate the appropriate interrupt handler and transfers control to that section of code.

The IVT plays a vital role in managing interrupt handling within the BIOS. It ensures that hardware interrupts, such as keyboard input or disk operations, are promptly addressed and that software programs can access the necessary system services. By efficiently managing interrupts, the IVT enables smooth operations and timely responses in computer systems.

Understanding the structure and organization of the BIOS Interrupt Vector List is essential for system programmers and developers. It provides them with the knowledge and tools to effectively utilize interrupt handling in their software, optimizing system performance and stability.

In the next section, we will delve deeper into the intricacies of the BIOS Interrupt Vector List, exploring its organization and the specific functions of interrupt handlers.

BIOS Processor Instructions

INTAddressTypeFunction Description
00h0000:0000hProcessorDivide Error
01h0000:0004hProcessorSingle Step
02h0000:0008hProcessorNon-maskable interrupt
03h0000:000ChProcessorBreakpoint instruction
04h0000:0010hProcessorOverflow instruction
05h0000:0014hBIOS ProcessorPrint screen Bound range exceeded
06h0000:0018hProcessorInvalid opcode
07h0000:001ChProcessorCoprocessor not available
08h0000:0020hHardware ProcessorIRQ 0 – System timer Interrupt out of range exception
Double exception
09h0000:0024hHardware ProcessorIRQ 1 – Keyboard Coprocessor segment overrun
0Ah0000:0028hHardware ProcessorIRQ 2 – General adapter use/Cascade Invalid Task State Selector
0Bh0000:002ChHardware ProcessorIRQ 3 – Serial port (COM2) Segment not present
0Ch0000:0030hHardware ProcessorIRQ 4 – Serial port (COM1) Stack exception
0Dh0000:0034hHardware ProcessorIRQ 5 – General adapter use Segment overrun exception General protection fault
0Eh0000:0038hHardware ProcessorIRQ 6 – Diskette controller Page fault
0Fh0000:003ChHardwareIRQ 7 – Parallel port (LPT1)
10h0000:0040hBIOS ProcessorVideo services
Coprocessor error
11h0000:0044hBIOS ProcessorEquipment list service
Alignment check
12h0000:0048hBIOS ProcessorMemory size service
Machine check
BIOS Processor Instructions

BIOS Instructions

INTAddressTypeFunction Description
13h0000:004ChBIOSFloppy/Hard disk services
14h0000:0050hBIOSSerial communications services
15h0000:0054hBIOSSystems services
16h0000:0058hBIOSKeyboard services
17h0000:005ChBIOSParallel printer services
18h0000:0060hBIOSROM BASIC/Boot failure
19h0000:0064hBIOSBootstrap loader
1Ah0000:0068hBIOSTime-of-Day services
1Bh0000:006ChBIOS<CTRL >< Break>
1Ch0000:0070hBIOSUser timer tick service
BIOS Instructions

BIOS Hardware Instructions

INTAddressTypeFunction Description
1Dh0000:0074hBIOS DataVideo control parameter table
1Eh0000:0078hBIOS DataFloppy disk configuration table
1Fh0000:007ChBIOS DataVideo graphics table
Hardware Instructions

BIOS Software Instructions

INTAddressTypeFunction Description
20h-3Fh0000:0080h-0000:00FChSoftwareDOS interrupts
44h-45h0000:0110h-0000:0114hSoftware?
47h-49h0000:011Ch-0000:0124hSoftware?
4Bh-6Fh0000:012Ch-0000:01BChSoftware?
78h-FFh0000:01E0h-0000:03FChSoftware?
Software Instructions

Work In Progress