GATE CSE 1993 | Question: 7.8

Question

The root directory of a disk should be placed

• A. at a fixed address in main memory
• B. at a fixed location on the disk
• C. anywhere on the disk
• D. at a fixed location on the system disk
• E. anywhere on the system disk

Comments

@Arjun sir can you please explain this in combination of B and B+ trees which are used for faster access. B and B+ structures are stored in memory and input to those algorithm is root directory which is stored on disk. Is this how it works?

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System disk: Another name for a bootable diskette, a floppy disk (or CD-ROM) that a computer can use to boot the operating system (OS) if the hard drive fails to boot the OS.

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Each disk (e.g., C:\, D:\, an external USB drive) has its own independent root directory.

When you re install widnow , you do format your old system disk and install your window on this formated system disk without losing data of another disks.

If it would have been stored on system disk , you would have loose data across all disks after reinstalling windows.  

So option B

Answer 1

File system uses directories which are the files containing the name and location of other file in the file system. Unlike other file,directory does not store the user data. Directories are the file that can point to other directories. Root directory point to various user directory. So they will be stored in such a  way that user cannot easily  modify them. They should be placed at fixed location on the disk.

Correct Answer: $B$

Comments

Because in comments you are saying it should be "root directory at a fixed location in disk." in answer it says "at fixed location in system disk"

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Okay root directory is present at the fixed location on the disk. Root directory also has a special name. What about other directories, They can be present at anywhere in the disk?

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• ✅ At a fixed location on the disk — Correct.
• ❌ At a fixed location on the system disk — Incorrect, because the root directory exists on every filesystem, not only on the system disk.

Example :

Imagine your computer has:

C:  Windows
D:  Games
E:  USB

All three drives have:

C:\
D:\
E:\

If the root directory were only on the system disk, then D: and E: couldn't store folders and files independently, which is obviously not true.

Answer 2

The top directory in a file system. The root directory is provided by the operating system and has a special name; for example, in DOS systems the root directory is called \. The root directory is sometimes referred to simply as the root.

reference - https://www.webopedia.com/TERM/R/root_directory.html

so Option B is right option

Answer 3

Correct Answer: B. at a fixed location on the disk

Detailed Explanation:

1. Why on the disk: A root directory handles the core pointer mappings and file structures needed to index files and subfolders. Because it must retain this data when the machine powers down, it is written onto non-volatile secondary storage (the disk itself). Volatile main memory (RAM) loses data upon shutdown, ruling out option A.
2. Why a fixed location: When an Operating System (OS) mounts or initialises any file system, it requires a predictable entry point to begin traversing the folder structure. If the root directory moved dynamically every time, the system would get stuck trying to read basic directory tables. Standard legacy architectures (such as FAT) explicitly map specific, static logical sector numbers to house this data.
3. Why not options D & E (the system disk): Every independently formatted disk volume or external storage media (such as a USB thumb drive, partition, or supplementary hard disk drive) must carry its own local root directory to maintain its internal layout structure. It cannot rely exclusively on a separate "system disk".

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 Key Differences Between "System Disk" and "Disk"

The functional distinction between a System Disk and a standard Disk boils down to file roles and hardware persistence rather than physical design constraints.