Context switching in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to define context switching.

Operating Systems

Context switching is the process where the CPU switches from executing one [1] to another.

Drag options to blanks, or click blank then click option'

Afile

Bprocess

Cprogram

Dthread

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing 'process' with 'program' or 'thread'.

Thinking context switching involves files.

Context switching involves switching the CPU from one process to another to allow multitasking.

2fill in blank

medium

Complete the sentence about what is saved during context switching.

Operating Systems

During context switching, the CPU saves the [1] of the current process so it can resume later.

Drag options to blanks, or click blank then click option'

Astate

Bfile

Cmemory

Dpriority

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking the entire memory is saved.

Confusing state with file or priority.

The CPU saves the state of the current process, including registers and program counter, to resume it later.

3fill in blank

hard

Fix the error in the sentence about context switching overhead.

Operating Systems

Context switching is a fast operation with no [1] on system performance.

Drag options to blanks, or click blank then click option'

Amemory

Bpriority

Coverhead

Dbenefit

Attempts:

3 left

💡 Hint

Common Mistakes

Assuming context switching has no cost.

Confusing overhead with memory or priority.

Context switching causes overhead, which means it uses CPU time and can slow down system performance.

4fill in blank

hard

Fill both blanks to describe what the CPU saves and loads during context switching.

Operating Systems

The CPU saves the [1] of the current process and loads the [2] of the next process to run.

Drag options to blanks, or click blank then click option'

Astate

Bmemory

Dpriority

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up state with memory or priority.

Thinking the CPU loads memory instead of state.

The CPU saves the state of the current process and loads the state of the next process to continue execution.

5fill in blank

hard

Fill all three blanks to complete the explanation of context switching steps.

Operating Systems

First, the CPU saves the [1] of the current process, then it updates the [2] to point to the next process, and finally it loads the [3] of the next process.

Drag options to blanks, or click blank then click option'

Astate

Bprogram counter

Dmemory address

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing program counter with memory address.

Not realizing the state is saved and loaded.

Context switching involves saving the state of the current process, updating the program counter to the next process, and loading the state of the next process.

Practice

1. What is context switching in an operating system?

easy

A. The process of installing new software on the computer

B. The process of connecting to the internet

C. The process of formatting a hard drive

D. The process of saving and loading the state of tasks to switch between them

Solution

1. Step 1: Understand the role of context switching

   Context switching allows the CPU to switch between different tasks by saving the current task's state and loading another's.

2. Step 2: Identify the correct description

   Only The process of saving and loading the state of tasks to switch between them describes saving and loading task states, which matches the definition of context switching.

3. Final Answer:

   The process of saving and loading the state of tasks to switch between them -> Option D

4. Quick Check:

   Context switching = saving/loading task states [OK]

Hint: Context switching means saving and loading task states [OK]

Common Mistakes:

• Confusing context switching with software installation
• Thinking it relates to hardware formatting
• Mixing it up with network connection processes

2. Which of the following is the correct sequence during a context switch?

easy

A. Save current task state, load new task state

B. Load new task state, save current task state

C. Execute new task, then save current task state

D. Save new task state, execute current task

Solution

1. Step 1: Understand the order of operations in context switching

   The operating system first saves the current task's state so it can resume later.

2. Step 2: Load the new task's state after saving the current one

   After saving, it loads the new task's state to start or continue its execution.

3. Final Answer:

   Save current task state, load new task state -> Option A

4. Quick Check:

   Save then load = correct sequence [OK]

Hint: Always save current state before loading new one [OK]

Common Mistakes:

• Loading new task before saving current state
• Executing tasks before saving or loading states
• Saving new task state instead of current task

3. Consider this simplified pseudocode for context switching:

current_task_state = save_state()
next_task_state = load_state()
execute(next_task_state)

What happens if save_state() is skipped?

medium

A. The current task will resume correctly later

B. The current task's progress will be lost when switched out

C. The next task will not start

D. The CPU will shut down

Solution

1. Step 1: Analyze the role of save_state()

   This function saves the current task's progress so it can resume later without losing data.

2. Step 2: Consequence of skipping save_state()

   If skipped, the current task's progress is not saved, so it will lose its state and cannot resume properly.

3. Final Answer:

   The current task's progress will be lost when switched out -> Option B

4. Quick Check:

   Skipping save_state = lost progress [OK]

Hint: Skipping save_state loses current task progress [OK]

Common Mistakes:

• Assuming next task won't start
• Thinking CPU shuts down
• Believing current task resumes fine without saving

4. A programmer wrote this code snippet to simulate context switching:

def context_switch(current, next):
    load_state(next)
    save_state(current)

What is the error in this code?

medium

A. It loads the next task before saving the current task's state

B. It saves the current task twice

C. It does not load the current task's state

D. It uses wrong function names

Solution

1. Step 1: Review the order of operations in the code

   The code calls load_state(next) before save_state(current).

2. Step 2: Identify the correct order for context switching

   The current task's state must be saved before loading the next task's state to avoid losing progress.

3. Final Answer:

   It loads the next task before saving the current task's state -> Option A

4. Quick Check:

   Save current before load next [OK]

Hint: Save current task before loading next task [OK]

Common Mistakes:

• Ignoring the order of save and load
• Assuming function names are incorrect
• Thinking saving twice is the problem

5. An operating system uses context switching to manage 3 tasks: A, B, and C. Each switch takes 2 milliseconds. If each task runs for 10 milliseconds before switching, how much total time is spent switching contexts in one full cycle of running all three tasks once?

hard

A. 8 milliseconds

B. 4 milliseconds

C. 6 milliseconds

D. 10 milliseconds

Solution

1. Step 1: Count the number of context switches in one cycle

   Running tasks A, B, and C once means switching from A to B, then B to C. That's 2 switches.

2. Step 2: Calculate total switching time

   Each switch takes 2 ms, so total switching time = 2 switches x 2 ms = 4 ms. But after C finishes, switching back to A to start next cycle is also a switch, so total 3 switches x 2 ms = 6 ms.

3. Final Answer:

   6 milliseconds -> Option C

4. Quick Check:

   3 switches x 2 ms = 6 ms [OK]

Hint: Count all switches including last to first [OK]

Common Mistakes:

• Counting only two switches instead of three
• Multiplying by task run time instead of switch time
• Ignoring the switch back to the first task