Internal vs external fragmentation in Operating Systems - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to define internal fragmentation.

Operating Systems

Internal fragmentation occurs when allocated memory blocks have unused space inside the [1].

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

Amemory block

Bprocess

Cdisk

Dcache

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing internal fragmentation with external fragmentation.

Thinking fragmentation happens outside the allocated block.

Internal fragmentation happens when the memory allocated to a process is larger than what it actually needs, leaving unused space inside the allocated block.

2fill in blank

medium

Complete the sentence to define external fragmentation.

Operating Systems

External fragmentation happens when free memory is split into small [1] scattered around, making it hard to allocate large blocks.

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

Aprocesses

Bpages

Cblocks

Dfiles

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up blocks with processes or files.

Assuming external fragmentation is inside allocated blocks.

External fragmentation occurs when free memory is divided into small pieces scattered throughout, preventing allocation of large contiguous memory blocks.

3fill in blank

hard

Fix the error in the sentence describing internal fragmentation.

Operating Systems

Internal fragmentation wastes memory outside the allocated [1].

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

Ablock

Bmemory block

Cprocess

Ddisk

Attempts:

3 left

💡 Hint

Common Mistakes

Saying fragmentation happens outside the block.

Confusing internal with external fragmentation.

Internal fragmentation wastes memory inside the allocated memory block, not outside.

4fill in blank

hard

Fill both blanks to complete the sentence about fragmentation types.

Operating Systems

Internal fragmentation wastes space [1] the allocated block, while external fragmentation wastes space [2] allocated blocks.

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

Ainside

Boutside

Cbetween

Dunder

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up inside and outside.

Using 'under' which is not correct in this context.

Internal fragmentation is unused space inside allocated blocks. External fragmentation is free space scattered between allocated blocks.

5fill in blank

hard

Fill all three blanks to complete the explanation of fragmentation effects.

Operating Systems

Internal fragmentation occurs due to [1] allocation sizes, causing wasted space [2] blocks. External fragmentation happens when free memory is [3] into small pieces.

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

Afixed

Binside

Csplit

Dvariable

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing fixed and variable allocation sizes.

Mixing up inside and outside wasted space.

Not understanding how free memory is divided.

Internal fragmentation happens because of fixed allocation sizes, leaving wasted space inside blocks. External fragmentation occurs when free memory is split into small scattered pieces.

Practice

1. Which of the following best describes internal fragmentation in memory management?

easy

A. Wasted space outside allocated memory blocks

B. Wasted space inside allocated memory blocks

C. Memory lost due to hardware failure

D. Memory used by the operating system kernel

Solution

1. Step 1: Understand internal fragmentation

   Internal fragmentation happens when allocated memory blocks have unused space inside them because the block size is larger than the requested memory.

2. Step 2: Compare with external fragmentation

   External fragmentation is about wasted space outside allocated blocks, so it is different from internal fragmentation.

3. Final Answer:

   Wasted space inside allocated memory blocks -> Option B

4. Quick Check:

   Internal fragmentation = wasted space inside blocks [OK]

Hint: Internal = inside allocated blocks wasted space [OK]

Common Mistakes:

• Confusing internal with external fragmentation
• Thinking fragmentation is caused by hardware
• Mixing up allocated and free memory spaces

2. Which of the following statements about external fragmentation is syntactically correct?

easy

A. External fragmentation wastes space inside allocated blocks.

B. External fragmentation is caused by software bugs only.

C. External fragmentation means memory is fully used without gaps.

D. External fragmentation wastes space outside allocated blocks in free memory.

Solution

1. Step 1: Identify correct definition of external fragmentation

   External fragmentation refers to wasted space outside allocated blocks, scattered in free memory.

2. Step 2: Check other options for correctness

   The statement "External fragmentation wastes space inside allocated blocks" describes internal fragmentation. The claim that it is caused by software bugs only is incorrect, as it arises from repeated allocation and deallocation. The idea that memory is fully used without gaps is false, since fragmentation creates unusable gaps in free memory.

3. Final Answer:

   External fragmentation wastes space outside allocated blocks in free memory. -> Option D

4. Quick Check:

   External fragmentation = wasted free memory gaps [OK]

Hint: External = wasted space outside allocated blocks [OK]

Common Mistakes:

• Mixing internal and external fragmentation definitions
• Assuming fragmentation is only due to bugs
• Ignoring free memory gaps in external fragmentation

3. Consider a memory system where 5 blocks of size 10KB are allocated, but each request was for 8KB. What type of fragmentation is present and what is the total wasted memory?

medium

A. Internal fragmentation; 10KB wasted total

B. Internal fragmentation; 2KB wasted

C. Internal fragmentation; 10KB wasted inside each block

D. External fragmentation; 10KB wasted

Solution

1. Step 1: Calculate wasted space per block

   Each block is 10KB but only 8KB is used, so 2KB is wasted inside each block.

2. Step 2: Calculate total wasted memory

   With 5 blocks, total wasted = 5 blocks * 2KB = 10KB wasted inside allocated blocks, which is internal fragmentation.

3. Final Answer:

   Internal fragmentation; 10KB wasted total -> Option A

4. Quick Check:

   Internal fragmentation = wasted inside blocks total 10KB [OK]

Hint: Wasted inside allocated blocks = internal fragmentation [OK]

Common Mistakes:

• Confusing total wasted with per block wasted
• Mixing internal with external fragmentation
• Ignoring multiplication by number of blocks

4. A system has free memory blocks of sizes 5KB, 3KB, and 4KB scattered around. A process requests 6KB. Which problem is this an example of, and what is the main issue?

medium

A. External fragmentation; no single free block large enough

B. Internal fragmentation; wasted space inside allocated blocks

C. External fragmentation; all free blocks are too large

D. Internal fragmentation; process size is too small

Solution

1. Step 1: Analyze free memory blocks

   The free blocks are 5KB, 3KB, and 4KB. The process needs 6KB, but no single block is large enough (maximum 5KB < 6KB).

2. Step 2: Identify fragmentation type and issue

   Free memory total is 12KB > 6KB, but scattered into small non-contiguous blocks with none large enough, causing allocation failure. This is external fragmentation.

3. Final Answer:

   External fragmentation; no single free block large enough -> Option A

4. Quick Check:

   External fragmentation = scattered free blocks too small [OK]

Hint: External fragmentation = scattered free blocks too small [OK]

Common Mistakes:

• Confusing internal with external fragmentation
• Assuming process size is too small causes fragmentation
• Ignoring block sizes when allocating memory

5. A system uses fixed-size memory blocks of 4KB. A program requests 10KB. How does internal and external fragmentation affect this allocation, and what is the total wasted memory?

hard

A. Internal fragmentation wastes 4KB; external fragmentation wastes 2KB

B. Internal fragmentation wastes 2KB; external fragmentation wastes 4KB

C. Internal fragmentation wastes 2KB; external fragmentation wastes 0KB

D. Internal fragmentation wastes 0KB; external fragmentation wastes 2KB

Solution

1. Step 1: Calculate blocks needed and internal fragmentation

   10KB requires 3 blocks of 4KB each (total 12KB). The extra 2KB (12KB - 10KB) inside allocated blocks is internal fragmentation.

2. Step 2: Consider external fragmentation

   Since blocks are fixed and allocated contiguously, no free space outside allocated blocks is wasted here, so external fragmentation is 0KB.

3. Final Answer:

   Internal fragmentation wastes 2KB; external fragmentation wastes 0KB -> Option C

4. Quick Check:

   Internal fragmentation = 2KB; external = 0KB [OK]

Hint: Internal = leftover in allocated blocks; external = gaps outside [OK]

Common Mistakes:

• Miscounting blocks needed for allocation
• Confusing internal and external fragmentation amounts
• Assuming external fragmentation always occurs