L-2.2: What is Arrival, Burst, Completion, Turnaround, Waiting and Response time in CPU Scheduling

Summary

In this educational video, the host of Gate Smashers explains key concepts in CPU scheduling, crucial for solving numerical problems in the field. The script covers arrival time, burst time, completion time, turnaround time, waiting time, and response time, using a bank visit analogy for clarity. It differentiates between CPU-bound and IO-bound processes, emphasizing the importance of understanding these times for mastering CPU scheduling algorithms and solving related numerical problems effectively.

Takeaways

• 🕒 **Arrival Time**: The moment a process enters the ready queue, analogous to arriving at a bank at 11'O clock.
• ⏱️ **Burst Time**: The duration a process requires to be executed on the CPU, similar to the time taken to deposit money.
• 🏁 **Completion Time**: The point in time when a process finishes execution, like exiting the bank at 12'O clock.
• 🔄 **Turnaround Time**: The total time from arrival to completion, calculated as completion time minus arrival time, e.g., 12 - 11 equals 1 hour.
• ⌛ **Waiting Time**: The difference between turnaround time and burst time, representing the extra time spent waiting, not executing, like the time spent waiting in a queue.
• 💻 **CPU Bound vs. IO Bound**: Processes can be categorized as CPU intensive or IO intensive, affecting their execution and waiting times.
• 📊 **Understanding Formulas**: Key formulas include turnaround time (completion time - arrival time) and waiting time (turnaround time - burst time).
• 📈 **Importance in Exams**: These concepts are crucial for solving CPU scheduling problems in competitive exams like GATE.
• 🔎 **Analyzing Process Types**: Distinguishing between CPU bound and IO bound processes helps in understanding their impact on scheduling and performance.
• 📝 **Practical Application**: The script uses a bank visit analogy to explain CPU scheduling concepts, making them easier to understand.

Q & A

What is the definition of arrival time in CPU scheduling?

Arrival time is the point in time when a process enters the ready queue from the ready state, meaning it's the time at which a process starts waiting in the queue to be executed.

How is burst time different from arrival time?

Burst time refers to the duration a process requires to be executed on the CPU, while arrival time is the specific point in time when a process enters the ready queue.

Can you provide an example to illustrate the concept of burst time?

An example given in the script is depositing money at a bank. The burst time would be the 15 minutes it takes for the clerk to deposit the money into the account.

What is completion time in the context of CPU scheduling?

Completion time is the point in time when a process finishes its execution. In the bank example, it's when the customer exits the bank after the transaction is complete.

How is turnaround time calculated and what does it represent?

Turnaround time is calculated by subtracting the arrival time from the completion time. It represents the total time a process spends in the system from its arrival to completion.

What is the difference between turnaround time and burst time?

Turnaround time is the total time spent in the system, including waiting, while burst time is the actual execution time on the CPU.

What does waiting time signify in CPU scheduling?

Waiting time signifies the amount of time a process spends waiting for the CPU to become available after it has arrived in the ready queue. It's calculated as turnaround time minus burst time.

Why is response time important in CPU scheduling?

Response time is important as it measures the time taken for the first response or the first instance of CPU execution after a process's arrival. It indicates how quickly a process starts executing.

How is response time calculated according to the script?

Response time is calculated as the time at which a process first gets the CPU minus the arrival time. It's the time from arrival until the process begins execution.

What are the two types of processes mentioned in the script?

The two types of processes mentioned are CPU bound and IO bound. CPU bound processes are those that require significant CPU time for execution, while IO bound processes spend more time waiting for input/output operations.

Why do processes have different waiting times?

Processes have different waiting times because they may have to wait for resources such as the CPU or for input/output operations to complete, which can vary depending on the process's nature and system load.