File allocation methods (contiguous, linked, indexed) in Operating Systems - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the contiguous file allocation method?

Contiguous file allocation stores all the blocks of a file in consecutive locations on the disk. This makes reading the file fast because the disk head moves less.

beginner

How does linked file allocation work?

In linked allocation, each file is a linked list of disk blocks. Each block contains a pointer to the next block. This allows files to be stored anywhere on the disk but can be slower to access.

intermediate

What is the main advantage of indexed file allocation?

Indexed allocation uses an index block that contains pointers to all the file's blocks. This allows direct access to any block, improving speed and flexibility.

intermediate

What is a common problem with contiguous allocation?

Contiguous allocation can cause external fragmentation because files need continuous space, making it hard to find large enough free blocks as disk fills up.

intermediate

Why might linked allocation be slower than indexed allocation?

Linked allocation requires following pointers from one block to the next, which means reading multiple disk blocks sequentially. Indexed allocation allows direct access to any block via the index, speeding up access.

Which file allocation method stores file blocks in consecutive disk locations?

A Contiguous allocation

B Linked allocation

C Indexed allocation

D None of the above

Contiguous allocation stores all file blocks one after another in consecutive disk locations.

In linked allocation, what does each block contain?

A The file size

B An index of all blocks

C The entire file data

D A pointer to the next block

Each block contains a pointer to the next block, forming a linked list.

Which allocation method uses an index block to store pointers to file blocks?

A Indexed allocation

B Linked allocation

C Contiguous allocation

D Sequential allocation

Indexed allocation uses a special index block that holds pointers to all the file's blocks.

What is a major disadvantage of contiguous allocation?

A Slow access to file blocks

B External fragmentation

C Complex index management

D Pointers use extra space

Contiguous allocation can cause external fragmentation because files need continuous space.

Why is indexed allocation faster than linked allocation for random access?

A Because it stores blocks consecutively

B Because it uses pointers in each block

C Because it uses an index block for direct access

D Because it compresses file data

Indexed allocation allows direct access to any block via the index block, speeding up random access.

Explain the differences between contiguous, linked, and indexed file allocation methods.

Think about how files are stored and accessed on disk.

Describe a real-life situation where linked file allocation might be preferred over contiguous allocation.

Consider flexibility versus speed.