Following is not the feature/characteristics of Linked-List allocation of Files in a File system:

Correct option is B

In linked-list allocation, each file is stored as a linked sequence of disk blocks, where every block contains a pointer to the next block belonging to the same file. Since the blocks need not be contiguous, external fragmentation is avoided, but the major drawback is poor random access.
To access a particular block, the system may have to follow the pointers from the beginning of the file until it reaches the required block, making random access relatively slow. Therefore, the statement that random access is very fast is not a characteristic of linked-list allocation.
Information Booster
1. Basic Working of Linked-List Allocation
· A file is represented as a linked list of disk blocks.
· The directory entry generally stores the address of the first block and, in some implementations, information about the file.
· Each allocated block contains a pointer to the next block of that file.
· The blocks belonging to a file can be located anywhere on the disk.
2. Fragmentation
· Linked allocation eliminates the problem of external fragmentation because a file does not require a contiguous group of disk blocks.
· Free blocks located at different positions can be linked together to store a file.
· Some space within the final block may remain unused, resulting in internal fragmentation.
3. Block Pointer Overhead
· A portion of each disk block is occupied by the pointer to the next block.
· Consequently, not all bytes of a physical disk block are available for actual file data.
· If a block has size B bytes and the pointer requires P bytes, the effective data capacity is approximately B−PB-P bytes per block.
4. File Allocation Table (FAT)
· The pointer information can be maintained in a separate table called the File Allocation Table (FAT).
· FAT stores information about the next block associated with each disk block.
· This keeps the pointers out of the data blocks and allows the blocks themselves to be used entirely for file data.
· FAT is the allocation mechanism associated with FAT-based file systems, such as FAT12, FAT16 and FAT32.
5. Sequential Access
· Linked allocation is particularly suitable for sequential access.
· Once the first block is located, the pointer in each block identifies the next block.
· Thus, sequentially reading the entire file can proceed naturally through the chain.
Additional Knowledge
· Option (a) is correct: Since linked allocation does not require contiguous disk blocks, external fragmentation is avoided. However, unused space may remain in the final allocated block, causing internal fragmentation.
· Option (c) is correct: In conventional linked allocation, each block needs space for a pointer. Therefore, the portion available for file data is smaller than the complete physical block size.
· Option (d) is correct in the context of FAT: Moving the link information into a table in memory allows the file's block chain to be followed without storing the pointer inside every data block. However, FAT itself has memory-consumption and scalability considerations, particularly for very large volumes.
· Important comparison:
· Contiguous allocation: Excellent random access but suffers from external fragmentation.
· Linked allocation: Good sequential access, avoids external fragmentation, but poor random access.
· Indexed allocation: Supports direct/random access through an index block and avoids the need to follow a complete chain of data blocks.