Which IRQ does COM1 commonly use?

Which IRQ does COM1 commonly use?

• 8
• 4
• 6
• 3 

EXPLANATION

Interrupt request (IRQ) 4 is normally used for the first serial port, COM1. This is also the default interrupt for the third serial port.
In a computer, an interrupt request 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. Hardware interrupts are used to handle events such as receiving data from a modem or network card, key presses, or mouse movements.