分类： LINUX
2011-11-06 16:04:08
In computer science, a reference is a value that enables a program to indirectly access a particular data item, such as a variable or a record, in the computer's memory or in some otherstorage device. The reference is said to refer to the data item, and accessing those data is called dereferencing the reference.
A reference is distinct from the data itself. Typically, a reference is the physical address of where the data is stored in memory or in the storage device. For this reason, a reference is often called a pointer or address, and is said to point to the data. However a reference may also be the offset (difference) between the datum's address and some fixed "base" address, or an index into an array.
In computer programming, a callback is a reference to executable code, or a piece of executable code, that is passed as an argument to other code. This allows a lower-level software layer to call a subroutine (or function) defined in a higher-level layer.
An interrupt handler, also known as an interrupt service routine (ISR), is a callback subroutine in microcontroller firmware, operating system or device driver whose execution is triggered by the reception of an interrupt. Interrupt handlers have a multitude of functions, which vary based on the reason the interrupt was generated and the speed at which the interrupt handler completes its task.
An interrupt handler is a low-level counterpart of event handlers. These handlers are initiated by either hardware interrupts or interrupt instructions in software, and are used for servicing hardware devices and transitions between protected modes of operation such as system calls.
An interrupt vector is the memory address of an interrupt handler, or an index into an array called an interrupt vector table that contains the memory addresses of interrupt handlers. When an interrupt is generated, the processor saves its execution state via a context switch, and begins execution of the interrupt handler at the interrupt vector.
The Interrupt Descriptor Table (IDT) is a data structure used by the x86 architecture to implement an interrupt vector table. The IDT is used by the processor to determine the correct response to interrupts and exceptions.
Use of the IDT is triggered by three types of events: hardware interrupts, software interrupts, and processor exceptions, which together are referred to as "interrupts". The IDT consists of 256 interrupt vectors–the first 32 (0-31 or 00-1F) of which are reserved for processor exceptions.
