The interrupt vector table is a table of pointers to routines that handle interrupts, and it is located in the first 1K of accessible memory on PCs. There are 256 4-byte pointers in the table, and each interrupt number has a specific use. 16 of the vectors are reserved for the 16 IRQ lines. The interrupt vector table is also known as a dispatch table.
What is an Interrupt Vector Table?
An Interrupt Vector Table (IVT) is a table of pointers that point to routines that handle interrupts in a computer system. Interrupts are signals that are generated by hardware or software to interrupt the normal flow of execution of a program, and to request the system to perform a specific task. Interrupts are used to handle events such as input/output (I/O) operations, hardware faults, and software exceptions.
The IVT on a PC is located in the first 1 K of accessible memory and is made up of 256 4-byte pointers. Each pointer in the IVT points to a specific interrupt handler routine. The interrupt handlers are responsible for performing the necessary actions to handle the interrupt and then returning control to the interrupted program.
What is the Purpose of an Interrupt Vector Table?
The purpose of an IVT is to provide a way for the system to handle interrupts in a consistent and organized way. The IVT ensures that each interrupt is directed to the correct interrupt handler routine. The IVT also makes it easy to add new interrupt handlers or modify existing ones, as all that is required is to update the appropriate pointer in the table.
The IVT is used by the system to handle a variety of interrupts, including hardware interrupts, software interrupts, and exceptions. For example, when a user presses a key on the keyboard, it generates a hardware interrupt. The system uses the appropriate pointer in the IVT to direct the interrupt to the keyboard interrupt handler routine, which reads the key and stores it in the appropriate buffer.
What is a Dispatch Table?
A Dispatch Table is another name for an Interrupt Vector Table. The term “dispatch” refers to the process of routing an interrupt to the appropriate interrupt handler routine. The Dispatch Table is essentially a lookup table that maps interrupt requests to specific interrupt handlers.
The Dispatch Table is created during the system initialization process and is stored in memory. The Dispatch Table ensures that the system is able to respond to interrupts quickly and efficiently, by directing each interrupt request to the appropriate interrupt handler routine. The Dispatch Table also allows for easy expansion of the interrupt handling capabilities of the system, by providing a way to add new interrupt handlers as needed.
In conclusion
The Interrupt Vector Table is a crucial component of any computer system. It provides a way for the system to handle interrupts in a consistent and organized way, ensuring that each interrupt is directed to the correct interrupt handler routine. The Dispatch Table, which is another name for the Interrupt Vector Table, is a lookup table that maps interrupt requests to specific interrupt handlers. The Dispatch Table allows for easy expansion of the interrupt handling capabilities of the system, making it a critical component of any modern computer system.
