Semaphores (counting and binary) in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a binary semaphore initialized to 1.

Operating Systems

binary_semaphore = Semaphore([1])

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A2

B0

C1

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing binary semaphore to 0 causes immediate blocking.

Using negative values is invalid for semaphore initialization.

A binary semaphore is initialized to 1 to indicate that the resource is available.

2fill in blank

medium

Complete the code to initialize a counting semaphore with 5 available resources.

Operating Systems

counting_semaphore = Semaphore([1])

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A5

B0

C1

D-5

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing counting semaphore to 0 blocks all threads initially.

Negative initialization values are invalid.

A counting semaphore initialized to 5 means 5 resources are available for concurrent access.

3fill in blank

hard

Fix the error in the code to correctly wait (P operation) on a semaphore.

Operating Systems

semaphore.[1]()

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Asignal

Bwait

Crelease

Dpost

Attempts:

3 left

💡 Hint

Common Mistakes

Using signal() or post() instead of wait() causes incorrect semaphore behavior.

Confusing wait() with release() method.

The wait() method is used to decrement the semaphore and block if the resource is unavailable.

4fill in blank

hard

Fill both blanks to correctly signal (V operation) a semaphore and update the resource count.

Operating Systems

semaphore.[1]()
resource_count [2] 1

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Asignal

B+=

C-=

Dwait

Attempts:

3 left

💡 Hint

Common Mistakes

Using wait() instead of signal() causes deadlock.

Decreasing resource count after signaling is incorrect.

The signal() method releases the semaphore, and the resource count increases by 1.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps resource names to their availability status using a binary semaphore.

Operating Systems

availability = [1]: semaphore.[2]() == 1 for [3] in resources

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A{resource

Bwait

Cresource

D[resource

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets instead of curly braces creates a list, not a dictionary.

Using signal() instead of wait() changes semaphore state incorrectly.

This dictionary comprehension checks if each resource is available by waiting on its semaphore and maps the resource name to a boolean.