The following four requests could come in to the operating system as it is running on computer system:
1. Clock in computer has just "ticked", and we require to update seconds counter.
2. The program running on processor 2 is attempting to do the illegal operation code.
3. Someone pulled the plug on power supply, and system will run out of power in 50 msec.
4. Disk has just read character which passed under read/write head, and it wishes to store it in memory before next one arrives.
In what order must operating system takle these requests and why in that order?