(This is the older material - click here - for current specification content)

9. Typical jobs

Consider a computer is running these jobs

1. A job that is copying files from one folder to another
2. A music player
3. An accounting application

Which would have the highest priority?

Answer:

If the 'shortest burst' algorithm is being used, then job 1 gets the highest priority because it will be heavily bottle-necked by the input-output time as it waits for the hard disk to respond between file copies.

If the Round Robin method was used, then each would have an equal time slice of CPU time

If the 'Priority' algorithm is used then it depends on their relative priority settings within their Process Control Block (PCB).

Which one is actually used?

This is not clear, as it depends on who coded the operating system's scheduler. Perhaps they were clever enough to take on board all three approaches (or more), depending on what is happening in the CPU and peripherals,

At the end of the day, it is down to the ingenuity of the operating systems' programmers as to which algorithm they choose to activate under which circumstance. As most operating systems are private (i.e. proprietary) then we cannot really know what they have coded. Suffice it to say that they must all deal with multiple processes running in memory.