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# Difference between Turn Around Time (TAT) and Waiting Time (WT) in CPU Scheduling

In CPU Scheduling, we often need to find the average Turnaround and Waiting Time with the help of Arrival, Burst and Completion Time. Let’s have a brief look of them: Turnaround Time (TAT):

1. It is the time interval from the time of submission of a process to the time of the completion of the process.
2. The difference b/w Completion Time and Arrival Time is called Turnaround Time.

Completion Time (CT): This is the time when the process completes its execution. Arrival Time (AT): This is the time when the process has arrived in the ready state.

`TAT = CT - AT`

Waiting Time (WT):

1. The time spent by a process waiting in the ready queue for getting the CPU.
2. The time difference b/w Turnaround Time and Burst Time is called Waiting Time.

Burst Time (BT): This is the time required by the process for its execution.

`WT = TAT - BT`

Now with Waiting Time and Burst Time, we can also calculate Turn Around Time via:

`TAT = BT + WT`

Example:

Solution: Figure – Gantt Chart

```Avg. TAT = (24 + 27 + 31) / 3 = 27.33 sec
Avg. WT  = (0 + 24 + 27) / 3 = 17.0 sec ```

Letâ€™s see the difference between Turnaround Time and Waiting Time:

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