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.
Index
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
| INT | Address | Type | Function Description |
|---|---|---|---|
| 00h | 0000:0000h | Processor | Divide Error |
| 01h | 0000:0004h | Processor | Single Step |
| 02h | 0000:0008h | Processor | Non-maskable interrupt |
| 03h | 0000:000Ch | Processor | Breakpoint instruction |
| 04h | 0000:0010h | Processor | Overflow instruction |
| 05h | 0000:0014h | BIOS Processor | Print screen Bound range exceeded |
| 06h | 0000:0018h | Processor | Invalid opcode |
| 07h | 0000:001Ch | Processor | Coprocessor not available |
| 08h | 0000:0020h | Hardware Processor | IRQ 0 – System timer Interrupt out of range exception Double exception |
| 09h | 0000:0024h | Hardware Processor | IRQ 1 – Keyboard Coprocessor segment overrun |
| 0Ah | 0000:0028h | Hardware Processor | IRQ 2 – General adapter use/Cascade Invalid Task State Selector |
| 0Bh | 0000:002Ch | Hardware Processor | IRQ 3 – Serial port (COM2) Segment not present |
| 0Ch | 0000:0030h | Hardware Processor | IRQ 4 – Serial port (COM1) Stack exception |
| 0Dh | 0000:0034h | Hardware Processor | IRQ 5 – General adapter use Segment overrun exception General protection fault |
| 0Eh | 0000:0038h | Hardware Processor | IRQ 6 – Diskette controller Page fault |
| 0Fh | 0000:003Ch | Hardware | IRQ 7 – Parallel port (LPT1) |
| 10h | 0000:0040h | BIOS Processor | Video services Coprocessor error |
| 11h | 0000:0044h | BIOS Processor | Equipment list service Alignment check |
| 12h | 0000:0048h | BIOS Processor | Memory size service Machine check |
BIOS Instructions
| INT | Address | Type | Function Description |
|---|---|---|---|
| 13h | 0000:004Ch | BIOS | Floppy/Hard disk services |
| 14h | 0000:0050h | BIOS | Serial communications services |
| 15h | 0000:0054h | BIOS | Systems services |
| 16h | 0000:0058h | BIOS | Keyboard services |
| 17h | 0000:005Ch | BIOS | Parallel printer services |
| 18h | 0000:0060h | BIOS | ROM BASIC/Boot failure |
| 19h | 0000:0064h | BIOS | Bootstrap loader |
| 1Ah | 0000:0068h | BIOS | Time-of-Day services |
| 1Bh | 0000:006Ch | BIOS | <CTRL >< Break> |
| 1Ch | 0000:0070h | BIOS | User timer tick service |
BIOS Hardware Instructions
| INT | Address | Type | Function Description |
|---|---|---|---|
| 1Dh | 0000:0074h | BIOS Data | Video control parameter table |
| 1Eh | 0000:0078h | BIOS Data | Floppy disk configuration table |
| 1Fh | 0000:007Ch | BIOS Data | Video graphics table |
| … | … | … | … |
BIOS Software Instructions
| INT | Address | Type | Function Description |
|---|---|---|---|
| … | … | … | … |
| 20h-3Fh | 0000:0080h-0000:00FCh | Software | DOS interrupts |
| … | … | … | … |
| 44h-45h | 0000:0110h-0000:0114h | Software | ? |
| … | … | … | … |
| 47h-49h | 0000:011Ch-0000:0124h | Software | ? |
| … | … | … | … |
| 4Bh-6Fh | 0000:012Ch-0000:01BCh | Software | ? |
| … | … | … | … |
| 78h-FFh | 0000:01E0h-0000:03FCh | Software | ? |