TRAP TRAP is the internal interrupt with the greatest priority among all interrupts, with the exception of division by zero. If a divide-by-zero error occurs, this interrupt is also triggered.
Definition A "trap" is a signal generated by a user application that instructs the operating system to execute certain activity instantly, whereas a "interrupt" is a signal generated by hardware that alerts the CPU to an occurrence that requires immediate attention. For example, pressing the Ctrl+C key combination will send a SIGINT signal to all processes running on your computer; this occurs when you want to stop something quickly (in this case, any running programs). SIGTRAP signals are sent out automatically when a process creates or changes an extension attribute in its data structure, such as the end of input on a file descriptor. They can also be sent out manually by the TRAP instruction. Interrupts are always delivered immediately, while traps may be delayed.
A software-generated interrupt is referred to as a trap. To avoid the requirement for device polling, an interrupt can be used to notify the completion of an I/O. A trap can be used to invoke operating system processes or detect arithmetic problems. Interruptions are hardware-initiated interrupts, whereas traps are software-initiated interrupts. Traps are usually only used by debugging tools or when a program needs to trigger an interruption in itself.
A trap is a type of interrupt that is more frequently known as a software interrupt. An interrupt is a broader phrase that encompasses both hardware interrupts (interruptions generated by hardware devices) and software interrupts (interrupts from software, such as traps). Traps are usually associated with system calls; although they can also be associated with other types of I/O operations. Hardware interrupts are usually mandatory while software interrupts may be voluntary or even ignored in some cases.
A software interrupt must be handled by the operating system. The only way for the CPU to notify the operating system that it needs service is by raising an exception. This can either be done directly by raising an exception or by using an instruction within the CPU's instructions set. If an exception is not handled immediately then the CPU will trigger a hardware interrupt which will cause the operating system to be notified of the problem.
Hardware interrupts are usually necessary for real-time tasks like timer interrupts or device driver interrupts. These types of interrupts cannot be delayed until later because the interruption might not be able to be resolved at all if it is not dealt with promptly. For this reason, they must be handled immediately by the operating system rather than being passed over temporarily and dealt with later. Hardware interrupts can also be used by CPUs that support nested interrupts; this feature allows multiple interrupt sources to share a single interrupt vector.
There are two kinds of events: traps and interruptions. A trap is triggered by a user application, whereas an interrupt is triggered by a hardware device such as a keyboard, timer, or other device. Control is passed to the trap handler by a trap, and control is passed to an interrupt handler by an interrupt. Traps are usually used for debugging purposes, while interrupts are used for real-time response to equipment changes or other such events.
Interrupts that can be deactivated or ignored by the CPU are classified as maskable or non-maskable. The TRAP interrupt is a non-maskable interrupt. It is employed in critical power loss scenarios and comprises of both level and edge triggering. The TRAP interrupt has a fixed location in the I/O port space of the processor. This means that whenever it occurs, the processor stops what it is doing and takes action.
The TRAP interrupt can only be disabled through a system reset. This prevents any undesirable behavior when it is used in situations where inactivation is necessary but a full reboot is not. Disabling the TRAP interrupt allows you to complete certain tasks without being interrupted by it.
Critical power loss conditions may arise for several reasons. In some cases, damage to the motherboard itself may have caused it to generate a high voltage spike that will destroy data if it remains on the chip. In other cases, radio frequency (RF) interference from other devices such as wireless phones may cause electrical currents to flow in the wrong direction inside the computer casing, which could also result in total device failure. A third reason may be that there is not enough power coming into the unit, so the CPU needs to go into sleep mode to preserve energy. When this happens, the TRAP interrupt is triggered so that the CPU can wake up once power is restored.
Interruptions and traps are inextricably linked. Traps are a form of exception, while interruptions are a type of exception. Intel x86 classifies events into two categories that overlap: vectored events (interrupts vs. exceptions) and exception classes (faults vs. traps vs. aborts). Interrupts are signals to the CPU that cause it to transfer control to a different location in its instruction stream.
Interrupt signals generated by programs are referred to as "software interrupts." A software interrupt can also be referred to as a trap or an exception. A signal alerts a program to the occurrence of an event. In this case, the event is the arrival of a computer virus.
Software interrupts can be divided into two categories: external and internal. An external software interrupt comes from a device such as a modem or network card that sends a signal to the computer requesting a program to stop what it is doing and start another program or perform some other task. Internal software interrupts are generated within the computer by devices such as memory chips or disk drives that detect some condition within themselves that should not occur at normal operation times. For example, if a block of memory becomes corrupted, a hardware interrupt will be triggered so that the system can attempt to fix the problem by either restoring the bad sector from an alternative copy of the data or replacing the damaged chip with a new one.
External software interrupts are usually caused by devices such as modems or networks cards which communicate with the computer through a general-purpose input/output (I/O) bus. The I/O bus is the channel between the device and the processor that controls how information is passed back and forth. When an external software interrupt occurs, it takes control of the processor and starts executing instructions in the Interrupt Vector Table (IVT).