On devices that do not use a PS/2 mouse, this interrupt is almost always used by the serial mouse. This is also the default interrupt for the third serial port (COM3). This interrupt is the first choice that most sound cards make when looking for an IRQ setting.
Keeping this in view, what is an IRQ number?
In a computer, an interrupt request (or IRQ) is a hardware signal sent to the processor that temporarily stops a running program and allows a special program, an interrupt handler, to run instead. Interrupt lines are often identified by an index with the format of IRQ followed by a number.
What is a IRQ conflict?
When two or more devices use the same interrupt line (and the same IRQ number) it's either "Interrupt Sharing" or an "Interrupt Conflict". The PCI bus allows all PCI devices to share interrupts with each other so this is called "sharing".
What is an IRQ assignment?
IRQ stands for Interrupt ReQuest and refers to special numbered channels that are used by devices to get the processors attention. For example, when you press a key on your keyboard it sends a signal to the processor via an IRQ channel (usually IRQ1) to let it know that it needs to process some data.