Day 02Part 03- Various types of times in Process Scheduling algorithm, Arrival, Burst TAT.

Day 02Part 03- Various types of times in Process Scheduling algorithm, Arrival, Burst TAT.

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 Day 02 | Part 03 – Process Scheduling Algorithm: Various Types of Times

Process scheduling in an operating system involves different types of times that determine the efficiency and execution sequence of processes. Let’s explore them one by one:

 Arrival Time (AT)

Definition: The time when a process enters the ready queue.
Example: If Process P1 arrives at time 0 ms and P2 at 2 ms, then:

• AT(P1) = 0 ms
• AT(P2) = 2 ms

 Burst Time (BT)

Definition: The total time required by a process to execute on the CPU.
 Also called Execution Time or CPU Time.
Example:

• P1 requires 5 ms to complete execution.
• P2 requires 8 ms to complete execution.
• So, BT(P1) = 5 ms, BT(P2) = 8 ms.

 Turnaround Time (TAT)

Definition: The total time taken by a process from arrival to completion.
Formula:

$$TAT=CompletionTime(CT)-ArrivalTime(AT)$$

Example: If a process arrives at 0 ms and completes at 10 ms, then:

• AT = 10 – 0 = 10 ms

 Waiting Time (WT)

Definition: The total time a process spends waiting in the ready queue before execution.
Formula:

$$WT=TurnaroundTime(TAT)-BurstTime(BT)$$

Example:

• If TAT = 10 ms, BT = 5 ms, then
• WT = 10 – 5 = 5 ms

 Completion Time (CT)

Definition: The time at which a process finishes execution.
Example: If process P1 finishes execution at 12 ms, then

• CT(P1) = 12 ms

 Response Time (RT)

Definition: The time from arrival to the first execution of a process.
Formula:

$$RT=FirstExecutionTime-ArrivalTime(AT)$$

Example:

• If a process arrives at 0 ms but starts execution at 3 ms, then
• RT = 3 – 0 = 3 ms

 Summary Table:

 Example Problem:

Given Processes:

If scheduled using FCFS (First Come First Serve), find TAT, WT, and RT.

Would you like me to solve this example step by step?

Day 02Part 03- Various types of times in Process Scheduling algorithm, Arrival, Burst TAT.

Operating System : Scheduling Algorithm – Jaunpur

PROCESSES AND CPU Scheduling

In Process Scheduling (a key topic in Operating Systems and commonly tested in GATE), understanding the various types of times is crucial. Below is a concise explanation of each important time type involved:

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1. Arrival Time (AT)

• Definition: The time at which a process enters the ready queue.

• Example: If a process arrives at time 0, its Arrival Time is 0.

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2. Burst Time (BT) / Execution Time

• Definition: The total time required by a process to execute on CPU.

• Note: It does not include time spent waiting.

• Example: If a process needs 5 ms of CPU time, its Burst Time is 5.

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3. Completion Time (CT)

• Definition: The time at which a process finishes execution.

• Example: If a process completes at time 12, its Completion Time is 12.

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4. Turnaround Time (TAT)

• Definition: The total time taken from arrival to completion.

• Formula:

  $$\text{TAT}=\text{CT}-\text{AT}$$

• Interpretation: How long a process stayed in the system.

• Example: If AT = 2, CT = 10 → TAT = 10 – 2 = 8

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5. Waiting Time (WT)

• Definition: The time a process spends in the ready queue, not running.

• Formula:

  $$\text{WT}=\text{TAT}-\text{BT}$$

• Example: If TAT = 8 and BT = 5 → WT = 8 – 5 = 3

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6. Response Time (RT)

• Definition: Time from arrival to first time the process gets CPU.

• Used in: Preemptive algorithms like Round Robin, SRTF, etc.

• Formula:

  $$\text{RT}=\text{First CPU Start Time}-\text{Arrival Time}$$

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Example Table for Clarification

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Would you like a solved example with Gantt chart for a specific scheduling algorithm (like FCFS, SJF, Round Robin)?

Day 02Part 03- Various types of times in Process Scheduling algorithm, Arrival, Burst TAT.

PROCESS SCHEDULING ALGORITHMS: A REVIEW

Chapter 5: Process Scheduling

Chapter 6: CPU Scheduling