Why cli and sti instructions are used during hooking aninterrupt?

Answer: Cli (Clear interrupt flag) and sti (set interrupt flag) instructions are used for clearing the flag and setting or enabling a flag respectively while hooking an interrupt.

Explanation: During the action of hooking an interrupt, there are certain interruptions while changing of real time interrupt vector and to avoid those interruptions two instructions are used that is cli ans sli. Cli is present for the clearing or disabling the interrupt flag and sti is used for setting or enabling a interrupt flag.