Turnaround Time Calculation Quiz and Flashcards: Uni-programming CPU Utilization

What is the impact of multiprogramming on the overall turnaround time of processes?

Which assumption about IO operations is made in the scenario described?

What is the reason behind the shortening of the overall turnaround time in multiprogramming?

In a scenario where one process is in a CPU burst and another is in an IO operation, what time is saved?

How does multiprogramming impact CPU utilization rate compared to uniprogramming?

What happens during an overlapped period of time in a multiprogramming scenario?

Which process's CPU burst begins first according to Formulation 1?

Why does the OS select one process in a CPU burst to use the CPU?

What is a benefit of having a multi-programming scenario?

Which assumption allows for selecting another process for CPU burst when the current one is doing IO operations?

Uni-programming System

In a uni-programming system, only one process is allowed to execute at a time, and the execution of the next process begins only after the previous one has completed.
CPU utilization rate is the proportion of time the CPU is doing useful work, which is 25% of the time in this case.
Overall turnaround time is the total time taken for all three processes to complete their execution, which is the sum of individual process's turnaround time.
In the given example, the overall turnaround time is 4 + 12 + 16 = 32 ms.

Characteristics of Processes

Process A, B, and C have turnaround times of 4, 12, and 16 ms, respectively.
Each process spends 25% of the time in CPU bursts and 75% in IO bursts.

CPU Utilization Rate

The CPU utilization rate is not affected by the order of execution of the three processes in a uni-programming system.
The CPU utilization rate is 25% in this case, which is calculated by the total time the CPU is being used divided by the overall turnaround time.

Multi-programming System

In a multi-programming system, the OS can execute multiple processes at the same time, and the CPU utilization rate is improved.
Assumptions in a multi-programming system include:
- Ignoring the time taken by the OS to do work in executing the processes.
- IO operations cannot happen in parallel.
- For each process, CPU burst must happen first.
The OS will execute all processes at the same time, and when one process is doing IO operations, the OS will select another process in CPU burst to use the CPU.
The overall turnaround time is shorter in a multi-programming system due to the overlapped period of time when one process is doing CPU and another is doing IO.

Calculate the CPU utilization rate and the overall turnaround time of three processes (A, B, and C) with specific characteristics when only one process is allowed to execute at a time (uni-programming). The processes have defined turn-around times, CPU burst and IO burst times.