Final answer:
In multiprogramming, the turnaround time for short jobs is typically faster due to efficient context switching, whereas for long jobs it is slightly increased because they might still need to wait for I/O operations.
Step-by-step explanation:
Under multiprogramming, turnaround time for short jobs is usually faster, and that for long jobs is slightly increased. Multiprogramming is a method of executing several jobs at the same time by holding them in memory. The operating system picks and begins to execute one of the jobs in memory.
If that job needs to wait for any I/O operation, the CPU starts executing another job. While long jobs can benefit from reduced wait times due to I/O overlap, short jobs are usually finished quicker as they can take advantage of frequent context switching, ensuring they don't have to wait for long I/O operations to complete before executing.