Free space management in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to describe free space management:
Free space management keeps track of {{BLANK_1}} on a storage device.

Operating Systems

Free space management keeps track of [1] on a storage device.

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

Afree space

Bused space

Cfile names

Dfile permissions

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing free space with used space.

Thinking it tracks file names or permissions.

Free space management is about tracking the free or unused space on a storage device so new files can be stored efficiently.

2fill in blank

medium

Complete the sentence:
One common method of free space management is the {{BLANK_1}} method, which uses a list to track free blocks.

Operating Systems

One common method of free space management is the [1] method, which uses a list to track free blocks.

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

Aindexed allocation

Blinked list

Ccontiguous allocation

Dbitmap

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing bitmap instead of linked list.

Confusing allocation methods with free space tracking methods.

The linked list method keeps a list of free blocks by linking them together, making it easy to find free space.

3fill in blank

hard

Fix the error in the statement:
The bitmap method uses a {{BLANK_1}} to represent each block's status as free or used.

Operating Systems

The bitmap method uses a [1] to represent each block's status as free or used.

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

Abit

Bfile descriptor

Clinked list

Dbyte

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing linked list which is a different method.

Choosing byte which is larger than needed.

The bitmap method uses a single bit for each block: 0 means free, 1 means used (or vice versa), making it efficient to track space.

4fill in blank

hard

Fill both blanks to complete the description:
In the bitmap method, each {{BLANK_1}} in the bitmap corresponds to a {{BLANK_2}} on the disk.

Operating Systems

In the bitmap method, each [1] in the bitmap corresponds to a [2] on the disk.

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

Abit

Bblock

Cfile

Ddirectory

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing file or directory with block.

Thinking bitmap uses bytes instead of bits.

Each bit in the bitmap represents one block on the disk, indicating if it is free or used.

5fill in blank

hard

Fill all three blanks to complete the code snippet for free space management:
free_space = {{BLANK_1}}(size)
for i in range(size):
    if free_space[{{BLANK_2}}] == 0:
        allocate_block({{BLANK_3}})

Operating Systems

free_space = [1](size)
for i in range(size):
    if free_space[[2]] == 0:
        allocate_block([3])

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

Abitarray

Bi

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using bitarray without importing or defining it.

Using wrong variable names instead of i.

This code creates a list to represent free space, checks each index i, and allocates the block at i if it is free (0).

Practice

1. What is the main purpose of free space management in an operating system?

easy

A. To manage user permissions for files

B. To speed up the CPU processing

C. To keep track of which parts of storage are free or used

D. To control network connections

Solution

1. Step 1: Understand the role of free space management

   Free space management is about tracking storage space availability.

2. Step 2: Identify the correct purpose

   It helps the system know which storage parts are free or occupied.

3. Final Answer:

   To keep track of which parts of storage are free or used -> Option C

4. Quick Check:

   Free space management = tracking free/used storage [OK]

Hint: Remember: free space management tracks storage availability [OK]

Common Mistakes:

• Confusing free space management with file permissions
• Thinking it manages CPU or network tasks
• Assuming it deletes files automatically

2. Which of the following is a common method used for free space management?

easy

A. Linked list

B. Binary search tree

C. Hash table

D. Stack

Solution

1. Step 1: Recall common free space management methods

   Common methods include bitmaps and linked lists to track free blocks.

2. Step 2: Identify the correct method

   Linked lists are widely used to keep track of free space blocks.

3. Final Answer:

   Linked list -> Option A

4. Quick Check:

   Common method = linked list [OK]

Hint: Linked lists or bitmaps track free space blocks [OK]

Common Mistakes:

• Choosing data structures not typically used for free space
• Confusing stacks or trees with free space tracking
• Assuming hash tables are used for free space management

3. Consider a bitmap representing free space where 1 means free and 0 means used: 10110010. Which blocks are free?

medium

A. Blocks 0, 2, 3, and 7

B. Blocks 0, 2, 3, and 6

C. Blocks 1, 3, 4, and 7

D. Blocks 1, 2, 5, and 6

Solution

1. Step 1: Understand bitmap indexing

   Bitmap bits index blocks starting at 0 from left to right: bit 0 = block 0.

2. Step 2: Identify bits with value 1

   Bitmap: 1(0),0(1),1(2),1(3),0(4),0(5),1(6),0(7). Blocks with 1 are 0, 2, 3, and 6.

3. Step 3: Verify bit 7

   Bit 7 is 0, so block 7 is used, not free.

4. Final Answer:

   Blocks 0, 2, 3, and 6 -> Option B

5. Quick Check:

   Bits 1 = free blocks 0,2,3,6 [OK]

Hint: Index bits from 0 left to right; 1 means free [OK]

Common Mistakes:

• Starting index from 1 instead of 0
• Mixing up bit positions and block numbers
• Confusing 0 and 1 meanings in bitmap

4. A linked list is used to track free blocks, but it sometimes skips some free blocks. What is the likely problem?

medium

A. The CPU cache is corrupted

B. The disk is full and no free blocks exist

C. The file system does not support linked lists

D. The linked list pointers are not updated correctly after allocation

Solution

1. Step 1: Understand linked list free space tracking

   Linked lists track free blocks by pointers linking them in order.

2. Step 2: Identify cause of skipping blocks

   If pointers are not updated after allocation or freeing, some free blocks may be skipped.

3. Final Answer:

   The linked list pointers are not updated correctly after allocation -> Option D

4. Quick Check:

   Incorrect pointer updates cause skipped free blocks [OK]

Hint: Check pointer updates after allocation to avoid skipping [OK]

Common Mistakes:

• Assuming disk is full without checking pointers
• Blaming file system support instead of pointer errors
• Confusing hardware issues with software pointer bugs

5. You have a disk with 100 blocks and a bitmap for free space. If the bitmap has 20 bits set to 1, what is the best way to allocate 5 new blocks efficiently?

hard

A. Scan the bitmap from start and pick the first 5 free blocks

B. Randomly pick any 5 blocks without checking bitmap

C. Allocate blocks only at the end of the disk

D. Delete existing files to free space first

Solution

1. Step 1: Understand bitmap allocation

   Bitmap shows which blocks are free (1) or used (0).

2. Step 2: Efficient allocation method

   Scanning bitmap from start to find first 5 free blocks is efficient and safe.

3. Final Answer:

   Scan the bitmap from start and pick the first 5 free blocks -> Option A

4. Quick Check:

   Scan bitmap for free blocks to allocate efficiently [OK]

Hint: Scan bitmap sequentially to find free blocks quickly [OK]

Common Mistakes:

• Picking blocks randomly without checking free status
• Assuming only end blocks can be allocated
• Deleting files unnecessarily before allocation